Couple of suggestions. First, try a reboot of both your router, followed by your Sonos speakers. Second, double check that your location is set properly on your account at www.sonos.com.

Finally, if neither of those help, I would recommend that you submit a system diagnostic within 10 minutes of recreating this problem, and call Sonos Support to discuss it. But don’t post the resulting diagnostic number here, they get sensitive about GDPR.

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 Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Thanks Bruce.

I'll see what happens and let you know 

Cheers Ian 

Hi Bruce 

Something has worked. Everything is back to normal. Thank you everyone who offered advice 

Cheers Ian