FIX!!! (Ish).  I have this exact problem and just fixed it!  One month ago my playbar stopped recognizing volume controls from both my apple remote and my Samsung tv remote.  I spoke to Sonos and was told that the IR receiver was likely toast and it can't be replaced.  By complete coincidence the Spanish power outage fried my legacy google Chromecast device so I upgraded to a Chromecast 4k.  Just for giggles I thought I would try to set it up with Sonos as my new remote.  It worked in a second and is flawless!!  The IR receiver is fine!  I'm still convinced that a software update impacted these remotes.  If you are having this issue, try a Chromecast remote!