I don't see Apple Music as an option in my Sonos system

I've got an iPad, iPhone and a Mac and Sonos set up and workging on all. I'm up to date with all Sonos controllers. iOS 9.3.1 on both iOS devices.

I have access to 2 Sonos systems.

I have signed up for Apple Music and it plays in iTunes on Mac and on both iOS devices.

Spotify works as a charm on both Sonos systems.

My problem is that I am not able to see Apple Music as an option when trying to 'Add Music Services' on either Sonos. Any ideas what could cause this?

Thank you.