I have a 7-year-old Playbar, two Play 1 surrounds, and a subwoofer connected to a Vizio TV and a relatively new Apple TV box for streaming (pretty sure it’s the non-4k version, probably 4 to 6 months old, and running TVOS 18). The TV audio output is turned off and uses the optical cable to connect to the Sonos Playbar. The Apple TV box is a replacement for an older Apple TV I wanted to use in another room, and has a silver remote that includes a power button, whereas the older remote is the thin black one with no power button.
Everything worked fine after upgrading the Apple TV box; my recollection is the Apple remote controlled the Sonos volume right out of the box.
Something happened that caused me to reconfigure our setup (I don’t recall what), so I did hard resets on all the Sonos equipment and set it all up from scratch, and following that the volume control on the new Apple Remote would no longer control the Sonos volume. The old Apple Remote DOES control the Sonos volume, so we've been getting by having to use both remotes. I've done that same hard reset and setup process at least three times to see if I could get the volume control to work, but no joy, in addition to several attempts at the remote setup in the Sonos app.
Here's what I've done so far. I've verified battery power on the Apple Remote. I've tried the remote setup numerous times, and it always tells me no signal from the remote was detected. Checked and there's no Apple software update available. I've tried the different remote-signal mechanisms available in the Apple TV Setting (I think it was set on Auto before, but I've tried really all the options available and none has made a difference).
What's most puzzling to me is that this exact hardware setup worked fine several months ago. I can't honestly remember what had changed when it stopped working, maybe TVOS version was different, but I'm not sure. If no one has any suggestions I think my next step may be a trip to the Apple Store to see if they have any way of verifying the remote is sending out a volume signal. The other thing I might do (although I don't relish doing this) is setting up the Apple TV box on another non-Sonos TV and see if volume control works on a different TV. But I'm not sure what exactly that may tell me.
Edit - I found
and do NOT see the red light as described in this post, so it looks like I may be buying a new remote.