Same issue here.... Another one. 

Maybe they removed the group functionality 

I have same problem!!!!

I have restarted all devices and the router.

And still the same issue.

I have no app update available and no firmware update too. So I should be on the latest version.

Please sort this mess!! 

At last I find that I should update Roam. Now sonos is working like before

Sorry - what is ‘update Roam’? I have the same issue.

I have the same problem.  All components are up to date.  I have two Era 300 and one Sonos One.  I can pair either Era to the One, but the Eras won’t group with each other.  Rebooted everything but I just get the same “unable to connect” error.

Roam is a sonos speaker. The comment said all speakers need to be up to date.