SONOS vanished after WiFi upgrade

I recently upgraded my wifi to google wifi after which all my SONOS speakers showed as ‘Unavailable’ in SmartThings.

I’ve deleted them all from the App, but now they can’t be refound. The search just spins. I’ve poked around and have tried various things other people have suggested such as hard-wiring a speaker into the wifi but to no avail.

Anybody any ideas??