LG Remote doesnt control volume with Arc

@Glen Moose you sir are a genius! I’ve tried all the other crazy fixes under the sun, re-accepting licenses, wiping to default, etc.
 

Didn’t try unplugging an HDMI switch I’d added in! Did that, then had to turn off both the Arc and the LGGx for a minute, powered back on and hey presto the tv actually detected it as a Sonos which I don’t recall happening before (might be something new on the latest firmware or I never had it set up properly). The tv setup on the Sonos worked straight away as well  

I’ve plugged everything else back in and it seems to continue working, so might be something to do with the order in which everything is plugged in, as I power cycled stuff when I plugged the hdmi switch in. 
 

Now I’ve got to go re-configure everything as I wiped to factory default. 
 

This was a top tip, thanks very much!

I may have spoken too soon. Even without the hdmi switch the problem reoccurs. It’s not just hdmi cec that’s messed up, the tv stops detecting the Sonos on startup and switches to internal speaker and I have to switch it back every time. It also breaks earc as a 4K disc with true hd downgrades audio to DD5.1. This all started for me after the last firmware update from LG. Truly risible software from LG. 

@Glen Moose 

I had the same exact adapter plugged into hdmi 4 with nothing on the other end. All better now. I love you.

I was able to get our system fixed by unplugging HDMI cables using Glens recommendation above but alas, the problem is back.  I unplugged all cables from the TV but the remote will still not control the volume anymore.  Anyone else having issues recently?

Same issue here. LG OLED65c1AUP. Universal Remote says Sonos is set up, shows volume + and minus, but no actual change in volume in Sonos Arc. Sonos app says there is an issue with HDMI and if I go through the fix steps it guides me through, I get an error message that CEC is not on while it is on. 

Hey guys,

I have the same problems with my Sony A90j, the Arc works quite well for some time but suddenly the volume control stops working or the Arc won’t output any sound at all.

I experienced similar behaviour as @Glen Moose, HDMI adapters (not connected to PC) or even my PS4 (which wasn’t even connected to power) were still detected by the Sony TV as input sources.

After disconnecting the adapter and the PS4, the Arc resumed to work normally.

First i thought this was a problem with my Sony TV but after reading that you guys have the same problem with your LG TV, it might well be a Sonos CEC problem.

Nevertheless, this problem has to be fixed since it is not bearable to disconnect all HDMI input souces every few days/weeks when the Arc decides to not work again…

Same here😟

Ya..pretty ridiculous Arc connects setup like a champ.volume control on lg 2021 c1 magic remote controls volume on arc for a few min..then bam..gone..I see the volume symbols as well on tv..bit no control all of a sudden .Tried everything on the forum..etc... 

My apologies..I think it's an lg thing..my firestick remote will control the volume regardless of what i plug into hdmi..but magic remote will stop adjusting the volume once i plug my firestick in..weird

I started experiencing this problem yesterday. I see the + and - on the OSD, but the remote does nothing. I am able to control the volume using the Sonos app.