After the 'update' on Nov 5 2020 my HDMI(ARC) has had a serious malfunction - no device connected. I have been using the HDMI(ARC) for over as year with no problems not even a slight glitch of line or area pixelation. I connected two (2) items that would be able to use the (ARC) to no avail. These very same two devices work in the other HDMI(S) but not the ARC HDMI. Anyone got some advice so I don't 'kill' the tv?
It could totally be an issue with the latest update on your TV. I can't say for sure, but on my TCL R617, back in April I had just bought a new sound bar and after several weeks with it, I could no longer use the TV's HDMI 3 input (which is ARC). I was trying everything I could to get the sound bar to work again with Atmos, mainly talking to Vizio about it as opposed to TCL/Roku. I really thought it was my sound bar for around a month (albeit, I tried different things on my TV as well), and then suddenly my TV updated and the ARC worked again and I have had no issues since.
So, I unfortunately cannot help, but I can only presume that it is the last update to your TV that's causing it, but I don't know. Hopefully, things work soon! I would just keep trying to put it out there that it isn't working. If you're like me, you'd keep researching to figure out a solution, and though I wouldn't want to discourage you from doing that, I feel somewhat confident that you're just going to have to wait for a fix on the TV side of things. The only thing I can recommend, but doubt it will work, is to go to your TV's input settings and change HDMI ARC to HDMI 2.0 if you haven't already.
I have recently got the 4K portion of my (ARC(HDMI3)) to work but somehow the HDR is not working. I have done 1) unplugged the tv for several minutes (did not work in re-establishing the (ARC)) 2) system restart did not re-establish the (ARC) 3) Factory reset. Yep that work in re-establishing the ARC in 4k but I have not re-gained the HDR10. 4) I have checked and re-checked for fresher updates for throughout the day (11/7/2020)