Same here

Same problem here.

Upgraded iPhone app a day or two ago, and have two SUB gen 2 or 3, bought from Sonos in 2021.
Yesterday I noticed that neither of the subs appeared in the app.

Ended up factory reseting both and add them again.
 

And got them back to the point that they at least now show in the app again, but as unregistered.

And registering them keeps failing.

Windows PC desktop Sonos app also act different, it only show a “Register products” and a “More alternatives” button, but none of the alternatives will let me see/control my Sonos speakers/zones. But that might be normal behavior when a speaker is not registered?

Thank you…What worked for me is to reset the app, under Account → App preferences → reset the app. I was then able to add my sub back to my system.  Clearly an app issue. Good luck!

Thanks for the tip, that resolved it for me too :)

Did not work for me.  My sub is on my network and LED is solid white.  It’s on a wired connection right now.  I hit the Fix It button, but it doesn’t Fix It.

After a bit of trial and error, I got my sub out of solid red LED state.  Still lots of issues with the new app connecting to the system.  Things go on and off line.  Sound shuts off on the beam in the bedroom and causes my wife to get upset.  Total disaster of an update.  I have unplugged my sub for now and that seems to make my system stable.  I am waiting for the next release and maybe I can get my sub working.

My biggest issue was when CSR told me my sub was now broken and I could send it back to Sonos for a 30% discount on a new sub since it is 3 years old and the warranty is 2 years.  I about lost it on that comment.  This was more than a week after the debacle started.  Support should be better informed than this.  

Anyone ever figure this out? Running into this connecting an older Play:3 and the Fix It button does nothing 

I recommend that you work with SONOS support for the PLAY:3 issue.