I’d try a few things first. Try rebooting your router, followed by your Sonos devices. Check for any potential wifi interference . Make sure all your Sonos devices are connected to the same subnet (although if it’s playing by itself, this may not be germane). If none of that works, submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Thanks for that… seems doable for a reluctant tech. Will let you know what happens. 
Cath

Did you ever get this resolved?  I’m having the same exact issue with a couple Play:1 speakers I’m trying to add to the system.

Ok, mine started working (so far).  When I added the speakers I did a factor reset first, then when I added them to the system it pushed an update to them, which I figured it would, but with nothing was working right, so I was poking around the app and decided to have it check for updates, even though it usually prompts me for them, and it had just done one not long ago.  But lo and behold it found an update.  Don’t know if it’s because of the new (old) speakers, or just a coincidence, but after doing a system update everything started working as expected and I can group things seamlessly between old and new speakers.

Hiya,

yep it worked albeit somewhat randomly. Can’t pinpoint to anything specific but the speaker just started working. 
 

gotta love technology!!!

After adding the Play:1’s I couldn’t group my Sonos Roam until I checked for and did an update on that as well.

So, for anyone having problems when adding Play:1’s to a system, it looks like not just the Play’s need updated to work with the system, but everything else in the system needs an update to know how to group to them.