When you say zones are you S1 or S2? Do you mean “multiple rooms”? What’s changed in your system or environment to cause them to go missing? Have you yet tried anything to recover them? Do you get any error mess?

Hi there.  Sorry, yes I mean multiple rooms (specifically kitchen, dining room and family room) are not visible on the app.  Nothing has changed in the system - it was all installed 5 years ago when we remodeled the house.  Most are speakers installed in the ceilings plus a soundbar and subwoofer in the family rooms.  I have not tried to recover them - would love any suggestions on how to do that.  Thanks.

What devices drive the speakers? Amp?

Whatever they are, I’d suggest unplugging them from power, together with your router. After a few minutes power up your router. When it is fully restarted and wifi is running, power up your (Amps?) sonos devices. Wait a few minutes and see if they’ve reappeared in your app. 

Use the Desktop app, the mobile app can’t be trusted to find all your devices.