I am having the same problem.
https://community.roku.com/t5/Discussions/TCL-65S401-PC-HDMI-No-Signal/td-p/942146
TCL Model 65S401
Hardware ID 7113X
Software Version 12.5.5 build 4174-30
Problem: My TV will no longer display a PC connected to HDMI Port 2 only displaying 'No Signal (is it on?)'
Context: I have had this PC-to-TV connection functioning for over a year with no issues. I have checked everything in Windows 11 and Nvidia control panel. My PC detects the TV just fine. I have moved all of the ports around. The TV displays a chromecast on port 3 fine. I have factory reset the TV.
I took an LG tv and plugged it in to the same HDMI cable to rule out the cable and PC and the LG displayed the PC input immediately with no issues. So it is not a problem on the input side.
Reading historical issues with these kinds of TVs it certainly seems like a software update broke this input connection somehow which is really really frustrating. I have spent hours troubleshooting this issue from every angle and the only one I don't have control over is bad TV software that updates automatically.
