There's been a wide scale attack on some Internet hosting services in the last day causing a number of issues around the world.
Currently, Spotify on Sonos is having some trouble with playback and connection as part of this. We're working with them on the issue and it's currently intermittent but we're actively monitoring it.
You may be unable to play Spotify on Sonos or songs might fail to play once started.
We're sorry for the trouble and will update you all when it's been resolved.