Hmm.. is the Apple Music App working okay for you - did you try reinstalling that App - if so also try a reset of the Sonos App in ‘Settings/App Preference’. The App will close just slide it off screen and on reopening go past the opening screens and accept the T&C’s etc and if prompted let it connect back to the existing Sonos System, although it may discover your system anyway and then try again.
The only other thing I can think of if that doesn’t work is to check your Country Settings in your Sonos proflle online by going here…
https://www.sonos.com/myaccount/user/profile/
Just make sure it’s correct and if that still fails, then within 20 minutes of trying/failing to connect the AM service in the Sonos App, submit a Sonos diagnostic report from the ‘Settings/Support’ area of the App. Make a note of the reference generated, and when practicable, contact/chat to Sonos Support Staff about the matter via this LINK and see what they can suggest to resolve the matter.
Hope that assists.