USB-C to HDMI stopped working after restart

[aario]

Hi Folks,
Debian 12. USB-C to HDMI was working with no problem.
I restarted my laptop for some reason. Now the monitor is black, saying there is no signal.
ls usb shows the usb device is there
dmesg shows normal messages:

Product: USB Type-C Digital AV Adapter
Manufacgturer: XXXXXX
SerialNumber: 000000000000000

But xrandr doesnot show the output anymore.

I also connected my samsung galaxy S to the usb end of the cable and the whole setup worked right away with no problem. The monitor, the cable, and the phone.

I have read many forum topics about isntalling displaylink driver or doing other changes. As a result I tried:

sudo apt install evdi
sudo resboot

But still it does not work. The fact is that it was working. So what has changed that suddenly the same computer cannot do what it was doing before the reboot? Can you point me to anything anywhere on how to trouble shoot it? Thanks in advance.

[Aki]

Hello,

Can you please report the output of the lsubs command?

Can you send the URL of its user manual ?

Did the USB-C to HDMI come with a kernel module (driver)?

When was the last time it worked?

May you analyse / share the file named /var/log/apt/history.log ?

[Alice Wilton]

My monitor's manual states that my monitor model may fail to "find" the signal if it is turned on after the computer was turned on.
It suggests to always turn on the monitor first and then turn on the computer.
I've experienced the problem once, pressing Control-Alt-F1 and then Control-Alt-F7 "fixed" it.