RPI with Octoprint won't recognize Ender 3 Pro (V2) anymore

What is the problem?

I had my printer connected to the RPI with Octoprint, and it was working perfectly. I added a BLTouch to the printer and thus, edited the Marlin 2.0 firmware and flashed to the SD card again. Since then, Octoprint has been giving me the same error.

What did you already try to solve it?

I have read other complaints about octoprint not being able to recognize the serial port due to incorrect USB connection. So, I tried multiple USB cables in order to solve it. Unfortunately, nothing has worked. I also checked the code from the Marlin 2.0 firmware to make sure I had the proper baudrate set for my particular printer. It is correct. There were other posts about the order in which I should power on the devices (i.e. first the RPI and its USB connection to the printer, then the power to the printer itself). I tried those options, with no luck either.

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.)

Changing monitoring state from "Offline" to "Opening serial connection"
Connecting to port /dev/ttyUSB0, baudrate 250000
Changing monitoring state from "Opening serial connection" to "Connecting"
Connected to: Serial<id=0x67adf470, open=True>(port='/dev/ttyUSB0', baudrate=250000, bytesize=8, parity='N', stopbits=1, timeout=10.0, xonxoff=False, rtscts=False, dsrdtr=False), starting monitor
Send: N0 M110 N0125
No answer from the printer within the connection timeout, trying another hello
Send: N0 M110 N0
125
There was a timeout while trying to connect to the printer
Changing monitoring state from "Connecting" to "Offline"
Connection closed, closing down monitor

Additional information about your setup

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

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