Can't connect to printer via serial

What is the problem?

No longer able to connect to Qidi XMAX via serial connection

What did you already try to solve it?

checking cables, updating and rebooting Octoprint plus performing other checks found in other topics in this forum

Have you tried running in safe mode and if so did it solve the issue?

yes and no it didn't

Complete Logs

octoprint.log, serial.log or output on terminal tab at a minimum, browser error console if UI issue ... no logs, no support! Not log excerpts, complete logs.)

octoprint.log

2020-11-21 01:00:01,017 - octoprint.startup - INFO - ******************************************************************************
2020-11-21 01:00:01,018 - octoprint.startup - INFO - Starting OctoPrint 1.4.2
2020-11-21 01:00:01,019 - octoprint.startup - INFO - ******************************************************************************
2020-11-21 01:00:01,430 - octoprint.util.connectivity.connectivity_checker - INFO - Connectivity state is currently: online
2020-11-21 01:00:01,431 - octoprint.util.connectivity.connectivity_checker - INFO - Connecting to 8.8.8.8:53 is working
2020-11-21 01:00:01,432 - octoprint.util.connectivity.connectivity_checker - INFO - Resolving octoprint.org is working
2020-11-21 01:00:01,445 - octoprint.startup - INFO - Unable to fetch plugin blacklist from https://plugins.octoprint.org/blacklist.json, proceeding without it: HTTPSConnectionPool(host='plugins.octoprint.org', port=443): Max retries exceeded with url: /blacklist.json (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0xb66a9150>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',))
2020-11-21 01:00:01,445 - octoprint.startup - INFO - Blacklist processing done
2020-11-21 01:00:01,490 - octoprint.plugin.core - INFO - Loading plugins from /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins, /home/pi/.octoprint/plugins and installed plugin packages...
2020-11-21 01:00:02,543 - octoprint.plugin.core - INFO - Found 19 plugin(s) providing 19 mixin implementations, 34 hook handlers
2020-11-21 01:00:02,675 - octoprint.server.heartbeat - INFO - Starting server heartbeat, 900.0s interval
2020-11-21 01:00:02,705 - octoprint.server - INFO - Intermediary server started
2020-11-21 01:00:02,706 - octoprint.plugin.core - INFO - Loading plugins from /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins, /home/pi/.octoprint/plugins and installed plugin packages...
2020-11-21 01:00:02,777 - octoprint.plugin.core - INFO - Found 19 plugin(s) providing 19 mixin implementations, 34 hook handlers
2020-11-21 01:00:02,795 - octoprint.filemanager.storage - INFO - Initializing the file metadata for /home/pi/.octoprint/uploads...
2020-11-21 01:00:02,799 - octoprint.filemanager.storage - INFO - ... file metadata for /home/pi/.octoprint/uploads initialized successfully.
2020-11-21 01:00:02,801 - octoprint.server - INFO - Added new permission from plugin action_command_notification: PLUGIN_ACTION_COMMAND_NOTIFICATION_SHOW (needs: u"Need(method='role', value=u'plugin_action_command_notification_show')")
2020-11-21 01:00:02,802 - octoprint.server - INFO - Added new permission from plugin action_command_notification: PLUGIN_ACTION_COMMAND_NOTIFICATION_CLEAR (needs: u"Need(method='role', value=u'plugin_action_command_notification_clear')")
2020-11-21 01:00:02,803 - octoprint.server - INFO - Added new permission from plugin action_command_prompt: PLUGIN_ACTION_COMMAND_PROMPT_INTERACT (needs: u"Need(method='role', value=u'plugin_action_command_prompt_interact')")
2020-11-21 01:00:02,804 - octoprint.server - INFO - Added new permission from plugin announcements: PLUGIN_ANNOUNCEMENTS_READ (needs: u"Need(method='role', value=u'plugin_announcements_read')")
2020-11-21 01:00:02,805 - octoprint.server - INFO - Added new permission from plugin announcements: PLUGIN_ANNOUNCEMENTS_MANAGE (needs: u"Need(method='role', value=u'plugin_announcements_manage'), Need(method='role', value=u'plugin_announcements_read')")
2020-11-21 01:00:02,806 - octoprint.server - INFO - Added new permission from plugin appkeys: PLUGIN_APPKEYS_ADMIN (needs: u"Need(method='role', value=u'plugin_appkeys_admin')")
2020-11-21 01:00:02,806 - octoprint.server - INFO - Added new permission from plugin backup: PLUGIN_BACKUP_ACCESS (needs: u"Need(method='role', value=u'plugin_backup_access')")
2020-11-21 01:00:02,807 - octoprint.server - INFO - Added new permission from plugin firmware_check: PLUGIN_FIRMWARE_CHECK_DISPLAY (needs: u"Need(method='role', value=u'plugin_firmware_check_display')")
2020-11-21 01:00:02,808 - octoprint.server - INFO - Added new permission from plugin logging: PLUGIN_LOGGING_MANAGE (needs: u"Need(method='role', value=u'plugin_logging_manage')")
2020-11-21 01:00:02,809 - octoprint.server - INFO - Added new permission from plugin pi_support: PLUGIN_PI_SUPPORT_STATUS (needs: u"Need(method='role', value=u'plugin_pi_support_check')")
2020-11-21 01:00:02,810 - octoprint.server - INFO - Added new permission from plugin pluginmanager: PLUGIN_PLUGINMANAGER_MANAGE (needs: u"Need(method='role', value=u'plugin_pluginmanager_manage')")
2020-11-21 01:00:02,811 - octoprint.server - INFO - Added new permission from plugin pluginmanager: PLUGIN_PLUGINMANAGER_INSTALL (needs: u"Need(method='role', value=u'plugin_pluginmanager_install'), Need(method='role', value=u'plugin_pluginmanager_manage')")
2020-11-21 01:00:02,812 - octoprint.server - INFO - Added new permission from plugin softwareupdate: PLUGIN_SOFTWAREUPDATE_CHECK (needs: u"Need(method='role', value=u'plugin_softwareupdate_check')")
2020-11-21 01:00:02,812 - octoprint.server - INFO - Added new permission from plugin softwareupdate: PLUGIN_SOFTWAREUPDATE_UPDATE (needs: u"Need(method='role', value=u'plugin_softwareupdate_update')")
2020-11-21 01:00:02,867 - octoprint.plugins.softwareupdate - INFO - Loaded version cache from disk
2020-11-21 01:00:03,561 - octoprint.util.pip - INFO - Using "/home/pi/oprint/bin/python2 -m pip" as command to invoke pip
2020-11-21 01:00:04,137 - octoprint.util.pip - INFO - Version of pip is 19.3.1
2020-11-21 01:00:04,139 - octoprint.util.pip - INFO - pip installs to /home/pi/oprint/lib/python2.7/site-packages (writable -> yes), --user flag needed -> no, virtual env -> yes
2020-11-21 01:00:04,139 - octoprint.util.pip - INFO - ==> pip ok -> yes
2020-11-21 01:00:04,144 - octoprint.plugin.core - INFO - Initialized 19 plugin implementation(s)
2020-11-21 01:00:04,157 - octoprint.plugins.psucontrol - INFO - Using GPIO for On/Off
2020-11-21 01:00:04,157 - octoprint.plugins.psucontrol - INFO - Using internal tracking for PSU on/off state.
2020-11-21 01:00:04,157 - octoprint.plugins.psucontrol - INFO - Running RPi.GPIO version 0.7.0
2020-11-21 01:00:04,158 - octoprint.plugins.psucontrol - INFO - Using GPIO for On/Off
2020-11-21 01:00:04,159 - octoprint.plugins.psucontrol - INFO - Configuring GPIO for pin 7
2020-11-21 01:00:04,161 - octoprint.plugin.core - INFO - 19 plugin(s) registered with the system:
|  Action Command Notification Support (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/action_command_notification
|  Action Command Prompt Support (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/action_command_prompt
|  Announcement Plugin (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/announcements
|  Anonymous Usage Tracking (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/tracking
|  Application Keys Plugin (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/appkeys
|  Backup & Restore (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/backup
|  Core Wizard (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/corewizard
|  Discovery (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/discovery
|  Error Tracking (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/errortracking
|  File Check (2020.8.7) (bundled) = /home/pi/oprint/local/lib/python2.7/site-packages/octoprint_file_check
|  Firmware Check (2020.9.23) (bundled) = /home/pi/oprint/local/lib/python2.7/site-packages/octoprint_firmware_check
|  GCode Viewer (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/gcodeviewer
|  Logging (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/logging
|  Login UI (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/loginui
|  Pi Support Plugin (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/pi_support
|  Plugin Manager (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/pluginmanager
|  PSU Control (0.1.9) = /home/pi/oprint/local/lib/python2.7/site-packages/octoprint_psucontrol
|  Software Update (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/softwareupdate
|  Virtual Printer (bundled) = /home/pi/oprint/lib/python2.7/site-packages/octoprint/plugins/virtual_printer
Prefix legend: ! = disabled, # = blacklisted, * = incompatible
2020-11-21 01:00:04,174 - octoprint.environment - INFO - Detected environment is Python 2.7.16 under Linux (linux2). Details:
|  hardware:
|      cores: 4
|      freq: 1500.0
|      ram: 1903980544
|  os:
|      id: linux
|      platform: linux2
|  plugins:
|      pi_support:
|          model: Raspberry Pi 4 Model B Rev 1.1
|          octopi_version: 0.17.0
|  python:
|      pip: 19.3.1
|      version: 2.7.16
|      virtualenv: /home/pi/oprint
2020-11-21 01:00:04,184 - octoprint.server - INFO - Reset webasset folder /home/pi/.octoprint/generated/webassets...
2020-11-21 01:00:04,202 - octoprint.server - INFO - Reset webasset folder /home/pi/.octoprint/generated/.webassets-cache...
2020-11-21 01:00:04,768 - octoprint.server - INFO - Shutting down intermediary server...
2020-11-21 01:00:05,212 - octoprint.server - INFO - Intermediary server shut down
2020-11-21 01:00:05,215 - octoprint.events - INFO - Processing startup event, this is our first event
2020-11-21 01:00:05,217 - octoprint.events - INFO - Adding 0 events to queue that were held back before startup event
2020-11-21 01:00:05,221 - octoprint.filemanager - INFO - Adding backlog items from all storage types to analysis queue...
2020-11-21 01:00:05,227 - octoprint.server.util.watchdog - INFO - Running initial scan on watched folder...
2020-11-21 01:00:05,233 - octoprint.server.util.watchdog - INFO - ... initial scan done.
2020-11-21 01:00:05,233 - octoprint.filemanager - INFO - Added 0 items from storage type "local" to analysis queue
2020-11-21 01:00:05,257 - octoprint.plugins.discovery - INFO - Registered 'OctoPrint instance on deuces-octopi' for _http._tcp
2020-11-21 01:00:05,276 - octoprint.plugins.discovery - INFO - Registered 'OctoPrint instance on deuces-octopi' for _octoprint._tcp
2020-11-21 01:00:05,324 - octoprint.server - INFO - Listening on http://127.0.0.1:5000
2020-11-21 01:00:05,409 - octoprint.plugins.pluginmanager - INFO - Loaded plugin repository data from disk, was still valid
2020-11-21 01:00:06,133 - octoprint.util.pip - INFO - Using "/home/pi/oprint/bin/python2 -m pip" as command to invoke pip
2020-11-21 01:00:06,183 - octoprint.util.pip - INFO - pip installs to /home/pi/oprint/lib/python2.7/site-packages (writable -> yes), --user flag needed -> no, virtual env -> yes
2020-11-21 01:00:06,242 - octoprint.util.pip - INFO - ==> pip ok -> yes
2020-11-21 01:00:06,271 - octoprint.plugins.softwareupdate - INFO - Minimum free storage across all update relevant locations is 26.0GB. That is considered sufficient for updating.
2020-11-21 01:00:06,486 - octoprint.plugins.pluginmanager - INFO - Loaded notice data from disk, was still valid
2020-11-21 01:00:06,597 - octoprint.server.preemptive_cache - INFO - Preemptively caching / (ui _default) for {'query_string': 'l10n=en', 'path': '/', 'base_url': 'http://192.168.1.84/'}
2020-11-21 01:00:12,036 - octoprint.server.preemptive_cache - INFO - ... done in 5.44s
2020-11-21 01:02:02,081 - octoprint.server.util.flask - INFO - Passively logging in user deuce4884 from ::ffff:10.8.0.2
2020-11-21 01:02:02,084 - octoprint.access.users - INFO - Logged in user: deuce4884
2020-11-21 01:02:06,092 - octoprint.server.util.sockjs - INFO - New connection from client: ::ffff:10.8.0.2
2020-11-21 01:02:06,329 - octoprint.server.util.flask - INFO - Passively logging in user deuce4884 from ::ffff:10.8.0.2
2020-11-21 01:02:06,329 - octoprint.access.users - INFO - Logged in user: deuce4884
2020-11-21 01:02:07,124 - octoprint.server.util.sockjs - INFO - User deuce4884 logged in on the socket from client ::ffff:10.8.0.2
2020-11-21 01:02:21,560 - octoprint.util.comm - INFO - Changing monitoring state from "Offline" to "Opening serial connection"
2020-11-21 01:02:21,564 - octoprint.util.comm - INFO - Connecting to port /dev/ttyAMA0, baudrate 115200
2020-11-21 01:02:21,573 - octoprint.util.comm - INFO - Changing monitoring state from "Opening serial connection" to "Connecting"
2020-11-21 01:02:51,624 - octoprint.util.comm - INFO - Changing monitoring state from "Connecting" to "Offline"
2020-11-21 01:02:51,635 - octoprint.plugins.action_command_notification - INFO - Notifications cleared
2020-11-21 01:03:04,974 - octoprint.util.comm - INFO - Changing monitoring state from "Offline" to "Detecting serial connection"
2020-11-21 01:03:04,994 - octoprint.util.comm - INFO - Serial detection: Performing autodetection with 4 port/baudrate candidates: /dev/ttyAMA0@115200, /dev/ttyAMA0@250000, /dev/ttyS0@115200, /dev/ttyS0@250000
2020-11-21 01:03:04,995 - octoprint.util.comm - INFO - Serial detection: Trying port /dev/ttyAMA0, baudrate 115200
2020-11-21 01:03:04,996 - octoprint.util.comm - INFO - Connecting to port /dev/ttyAMA0, baudrate 115200
2020-11-21 01:03:04,999 - octoprint.util.comm - INFO - Serial detection: Handshake attempt #1 with timeout 5.0s
2020-11-21 01:03:05,002 - octoprint.util.comm - INFO - M110 detected, setting current line number to 0
2020-11-21 01:03:10,009 - octoprint.util.comm - INFO - Serial detection: Handshake attempt #2 with timeout 5.0s
2020-11-21 01:03:10,018 - octoprint.util.comm - INFO - M110 detected, setting current line number to 0
2020-11-21 01:03:15,020 - octoprint.util.comm - INFO - Serial detection: Handshake attempt #3 with timeout 5.0s
2020-11-21 01:03:15,029 - octoprint.util.comm - INFO - M110 detected, setting current line number to 0
2020-11-21 01:03:20,040 - octoprint.util.comm - INFO - Serial detection: Trying port /dev/ttyAMA0, baudrate 250000
2020-11-21 01:03:20,044 - octoprint.util.comm - INFO - Serial detection: Handshake attempt #1 with timeout 5.0s
2020-11-21 01:03:20,051 - octoprint.util.comm - INFO - M110 detected, setting current line number to 0
2020-11-21 01:03:25,058 - octoprint.util.comm - INFO - Serial detection: Handshake attempt #2 with timeout 5.0s
2020-11-21 01:03:25,062 - octoprint.util.comm - INFO - M110 detected, setting current line number to 0
2020-11-21 01:03:30,069 - octoprint.util.comm - INFO - Serial detection: Handshake attempt #3 with timeout 5.0s
2020-11-21 01:03:30,079 - octoprint.util.comm - INFO - M110 detected, setting current line number to 0
2020-11-21 01:03:35,085 - octoprint.util.comm - INFO - Serial detection: Trying port /dev/ttyS0, baudrate 115200
2020-11-21 01:03:35,088 - octoprint.util.comm - INFO - Connecting to port /dev/ttyS0, baudrate 115200
2020-11-21 01:03:35,113 - octoprint.util.comm - ERROR - Unexpected error while connecting to serial port /dev/ttyS0, baudrate 115200 from hook default: SerialException: 'Could not configure port: (5, 'Input/output error')' @ comm.py:_open_serial:2784
Traceback (most recent call last):
  File "/home/pi/oprint/local/lib/python2.7/site-packages/octoprint/util/comm.py", line 2784, in _open_serial
    settings().getFloat(["serial", "timeout", "connection"]))
  File "/home/pi/oprint/local/lib/python2.7/site-packages/octoprint/util/comm.py", line 2761, in default
    serial_obj.open()
  File "/home/pi/oprint/local/lib/python2.7/site-packages/serial/serialposix.py", line 272, in open
    self._reconfigure_port(force_update=True)
  File "/home/pi/oprint/local/lib/python2.7/site-packages/serial/serialposix.py", line 326, in _reconfigure_port
    raise SerialException("Could not configure port: {}".format(msg))
SerialException: Could not configure port: (5, 'Input/output error')
2020-11-21 01:03:35,115 - octoprint.util.comm - INFO - Serial detection: Could not open port /dev/ttyS0, baudrate 115200, skipping
2020-11-21 01:03:35,120 - octoprint.util.comm - INFO - Serial detection: Trying port /dev/ttyS0, baudrate 250000
2020-11-21 01:03:35,122 - octoprint.util.comm - INFO - Connecting to port /dev/ttyS0, baudrate 250000
2020-11-21 01:03:35,128 - octoprint.util.comm - ERROR - Unexpected error while connecting to serial port /dev/ttyS0, baudrate 250000 from hook default: SerialException: 'Could not configure port: (5, 'Input/output error')' @ comm.py:_open_serial:2784
Traceback (most recent call last):
  File "/home/pi/oprint/local/lib/python2.7/site-packages/octoprint/util/comm.py", line 2784, in _open_serial
    settings().getFloat(["serial", "timeout", "connection"]))
  File "/home/pi/oprint/local/lib/python2.7/site-packages/octoprint/util/comm.py", line 2761, in default
    serial_obj.open()
  File "/home/pi/oprint/local/lib/python2.7/site-packages/serial/serialposix.py", line 272, in open
    self._reconfigure_port(force_update=True)
  File "/home/pi/oprint/local/lib/python2.7/site-packages/serial/serialposix.py", line 326, in _reconfigure_port
    raise SerialException("Could not configure port: {}".format(msg))
SerialException: Could not configure port: (5, 'Input/output error')
2020-11-21 01:03:35,131 - octoprint.util.comm - INFO - Serial detection: Could not open port /dev/ttyS0, baudrate 250000, skipping
2020-11-21 01:03:35,135 - octoprint.util.comm - INFO - Changing monitoring state from "Detecting serial connection" to "Error: No more candidates to test, and no working port/baudrate combination detected."
2020-11-21 01:03:35,149 - octoprint.util.comm - INFO - Changing monitoring state from "Error: No more candidates to test, and no working port/baudrate combination detected." to "Offline (Error: No more candidates to test, and no working port/baudrate combination detected.)"
2020-11-21 01:03:35,203 - octoprint.plugins.action_command_notification - INFO - Notifications cleared
2020-11-21 01:03:35,669 - octoprint.plugins.tracking - INFO - Sent tracking event commerror_autodetect, payload: {'commerror_text': u'No more candidates to test, and no working port/baudrate combination detected.'}

serial.log

2020-11-21 01:02:21,554 - Changing monitoring state from "Offline" to "Opening serial connection"
2020-11-21 01:02:21,568 - Connecting to port /dev/ttyAMA0, baudrate 115200
2020-11-21 01:02:21,573 - Changing monitoring state from "Opening serial connection" to "Connecting"
2020-11-21 01:02:21,575 - Connected to: Serial<id=0xaa479eb0, open=True>(port='/dev/ttyAMA0', baudrate=115200, bytesize=8, parity='N', stopbits=1, timeout=10.0, xonxoff=False, rtscts=False, dsrdtr=False), starting monitor
2020-11-21 01:02:51,612 - There was a timeout while trying to connect to the printer
2020-11-21 01:02:51,623 - Changing monitoring state from "Connecting" to "Offline"
2020-11-21 01:02:51,631 - Connection closed, closing down monitor
2020-11-21 01:03:04,972 - Changing monitoring state from "Offline" to "Detecting serial connection"
2020-11-21 01:03:04,993 - Performing autodetection with 4 port/baudrate candidates: /dev/ttyAMA0@115200, /dev/ttyAMA0@250000, /dev/ttyS0@115200, /dev/ttyS0@250000
2020-11-21 01:03:04,995 - Trying port /dev/ttyAMA0, baudrate 115200
2020-11-21 01:03:04,997 - Connecting to port /dev/ttyAMA0, baudrate 115200
2020-11-21 01:03:04,999 - Handshake attempt #1 with timeout 5.0s
2020-11-21 01:03:05,001 - Connected to: Serial<id=0xaa1b96b0, open=True>(port='/dev/ttyAMA0', baudrate=115200, bytesize=8, parity='N', stopbits=1, timeout=5.0, xonxoff=False, rtscts=False, dsrdtr=False), starting monitor
2020-11-21 01:03:05,003 - Send: N0 M110 N0*125
2020-11-21 01:03:10,008 - Handshake attempt #2 with timeout 5.0s
2020-11-21 01:03:10,020 - Send: N0 M110 N0*125
2020-11-21 01:03:15,019 - Handshake attempt #3 with timeout 5.0s
2020-11-21 01:03:15,031 - Send: N0 M110 N0*125
2020-11-21 01:03:20,040 - Trying port /dev/ttyAMA0, baudrate 250000
2020-11-21 01:03:20,044 - Handshake attempt #1 with timeout 5.0s
2020-11-21 01:03:20,053 - Send: N0 M110 N0*125
2020-11-21 01:03:25,057 - Handshake attempt #2 with timeout 5.0s
2020-11-21 01:03:25,069 - Send: N0 M110 N0*125
2020-11-21 01:03:30,068 - Handshake attempt #3 with timeout 5.0s
2020-11-21 01:03:30,081 - Send: N0 M110 N0*125
2020-11-21 01:03:35,084 - Trying port /dev/ttyS0, baudrate 115200
2020-11-21 01:03:35,094 - Connecting to port /dev/ttyS0, baudrate 115200
2020-11-21 01:03:35,112 - Unexpected error while connecting to serial port /dev/ttyS0, baudrate 115200 from hook default: SerialException: 'Could not configure port: (5, 'Input/output error')' @ comm.py:_open_serial:2784
2020-11-21 01:03:35,114 - Could not open port /dev/ttyS0, baudrate 115200, skipping
2020-11-21 01:03:35,117 - Trying port /dev/ttyS0, baudrate 250000
2020-11-21 01:03:35,123 - Connecting to port /dev/ttyS0, baudrate 250000
2020-11-21 01:03:35,127 - Unexpected error while connecting to serial port /dev/ttyS0, baudrate 250000 from hook default: SerialException: 'Could not configure port: (5, 'Input/output error')' @ comm.py:_open_serial:2784
2020-11-21 01:03:35,130 - Could not open port /dev/ttyS0, baudrate 250000, skipping
2020-11-21 01:03:35,134 - Changing monitoring state from "Detecting serial connection" to "Error: No more candidates to test, and no working port/baudrate combination detected."
2020-11-21 01:03:35,148 - Changing monitoring state from "Error: No more candidates to test, and no working port/baudrate combination detected." to "Offline (Error: No more candidates to test, and no working port/baudrate combination detected.)"
2020-11-21 01:03:35,178 - Connection closed, closing down monitor
2020-11-21 01:04:34,128 - Disabling serial logging

Additional information about your setup

OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ... as much data as possible

Octoprint Version 1.4.2, Version 0.17.0, running on Raspberry Pi 4 Model B Rev 1.1, Qidi XMAX, Chrome browser, Windows 10

I tried connecting with port and baud rate settings that I last connected with and after it didn't work I set it to AUTO but it still didn't work

You may have to install this plugin:

Also see this:

Installed it but no change. I never had to have it before either

Have you checked the USB cable, printer power on, etc?

of course the printer is on. it's connected through the UART

We are just trying to help and sometimes suggest things that have been issues elsewhere. There is a collection of printers that while their primary power is turned off, the controller board draws 5V power from the USB port and strange things happen.

Next, I assume you have read and digested Failed to auto detect serial port (Qidi X-pro).

Could you summarize how you are connecting to the printer, please. Your problem statement says "No longer able to connect to Qidi XMAX via serial connection" so I'm assuming you had it working sometime in the past. Can you summarize what has changed since then (i.e. OctoPi version, OctoPrint version when it worked)?

This may help us better understand what might have caused this issue.

nothing has changed since I last connected to it through octoprint. the last time i had a connecting issue it was because of emi on the cable and my terminal looked like encryption. I solved that issue by remaking the cable and using ferrite rings. didn't have an issue for a while but haven't tried connecting in months due to being busy with other things. powered it up the other day and tried to connect just as always with no success. i saw there were updates available so did that and tried again with no success.

Somewhere in the 1.4.x updates, Gina changed the connection logic. I don't know if that is the problem or if its something else but that's why I wanted to know.

I changed some things in the auto connect logic by making it more compatible, everything else has been untouched.