Try powering down (and unplugging)  all Sonos units. Then reboot your router. Give the router two minutes to reload, then plug back in / power up your Sonos devices.

If this doesn’t fix the issue, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. 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.

​@Airgetlam Thank you. That did the trick. All back up and running smoothly. Cheers.

You might prevent the issue in the future by setting static/reserved ip addresses for all Sonos using the router's DHCP page.

Agreed. That is the ‘more permanent’ version of what you’ve done. If your router can do it (mine, oddly, can not, but the previous one did). 

Amazing what features manufacturers decide are not needed. I'd really miss that ip feature if it went away, I find it really handy to have my servers with easy to remember IPs. That aside from my Sonos system being close to unusable without the IPs being static.

I wouldn’t call it amazing…more annoying. And to be honest, this router hasn’t done duplicate IPs yet, that I’m aware of. Although that could be a function of the number of power outages this island community seems to suffer. I’m still giving consideration in moving it to modem only functionality, and setting up my own router (new, when I figure out what I want).