So, you’re having issues with AirPlay 2, and not the Sonos controller? At least beyond Apple not allowing the Sonos client to create stations, of course?
My guess is you’re experiencing an issue local to your setup, but I’m unfamiliar enough with how AirPlay 2 connects to Sonos to be sure. I’d certainly try a reboot of all things, from the Apple device (power it down, then power it up, no need for reset), the router (never hurts to have a fresh load of the network) and the Sonos (also, never hurts to power cycle Sonos).
But if that doesn’t change anything, 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.