OctoPrint: Error: Failed to autodetect serial port, please set it manuall

What is the problem?

Setting up second raspberry pi B+ - installed octopi rel 16, all was well - shutdown pc and printer for several days. powered up PC and printer and am getting the following message when I try connecting to it in Octoprint Error: Failed to autodetect serial port, please set it manual

Please note that my other printer - ENDER 3 is woring with a separate raspberry PI B+ and is having no problems.

What did you already try to solve it?
When to Connections and tried to change it from AUTO but it only let me select AUTO.
Went to OctoPrint setting and also tried changing the serial detection from AUTO - no good
When to Server and tested the Port connectivity check and it testes out fine.
Tried changing the Printer profile thinking that perhaps it had been corrupted but no good.
Shutdown the raspberry PI and replaced the SD card with my backup SD card - no change

Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)
OctoPrint 1.3.10
Octopi 0.16.1
Ender 2
TH3D 1.R1.4
Terminal log:
Changing monitoring state from "Offline" to "Detecting serial port"
Serial port list: []
Changing monitoring state from "Detecting serial port" to "Error: Failed to autodetect serial port, please set it manually."
Failed to autodetect serial port, please set it manually.
Changing monitoring state from "Offline" to "Detecting serial port"
Serial port list: []
Changing monitoring state from "Detecting serial port" to "Error: Failed to autodetect serial port, please set it manually."
Failed to autodetect serial port, please set it manually.

Found the problem. Swapping connection cable from working raspberry pi to the one reporting the connection error and it worked. I have a bad cable.

Tried to mark this as solved but I get a 404 error ion the website.

(quoted to be able to mark as solved because Discourse doesn't allow marking the original post as the solution)

But not even with the 3D printer does octopi recognize the ttyUSB port!

OctoPrint will list the port if the operating system detects it. If the OS doesn't detect the printer on that port as a serial device, OctoPrint can't either.

But how can you make sure the OS detects the printer?