Same thing has happened to me twice. I am not sure what the solution is. But after a couple of days (up to 6 days) the problem stops. Perhaps it is because the Sonos component has been restarted?
It is a reoccurring problem, at I really hope Spotify is working hard on a solution. Next time it happens, I will drop my subscription to Spotify and go to another provider.
Cant offer much help other than the problem is only with the sonos player
Spotify plays fine in its stand alone mode and the internet radio works fine. Am not sure whether the integration to sonos has a firewall type of issue and am waiting from a response from sonos.
will bring you up to speed if i find out anything constructive to report
had same problem
just re-installed spotify software, restarted Sonos, done
i guess its a software version upgrade with spotify that they could do a better job communicating