The first thing I’d try is unplugging all Sonos devices from power, then rebooting your router. Only one the router comes back up should you plug them back in, and wait two minutes to test. 

However, if that doesn’t work, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it, or post the diagnostic number here for a Community Moderator to pick up.

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, there are more options available beyond just the diagnostic analysis.