I have old Play5 and One in my system. Apple TV, Sonos and IOS are all using the latest software versions. Every single device has been turned on and off many times and Bluetooth on/off too. All use the same 2.4 ghz wifi network. All devices within one meter of each other. Tried also to reset Sonos and create the Sonos system from scratch. Playing from Iphone works fine.
Strange thing is that when Apple TV was connected to 5 ghz network, Sonos showed up in Airplay. But refused to work obviously as my Sonos can connect only in 2.4 ghz network. Now in 2.4 ghz network, Sonos is not showing up in Airplay at all.
I have read the other discussions, tried everything I could find there. The problem persists.