Apple Music uploads won't play on Sonos

I have a music library on a NAS server consisting of ripped CDs and digitised vinyl.  All of these do play happily with some buffering via Music Library on Sonos.  I have recently started using Apple Music and have synced all the NAS music into Apple Music.  On my Sonos app on the Mac, it is all available and playable through Apple Music, but on the iPhone and iPad apps the album artwork and title is displayed but the tracks are all greyed out and unplayable.  If I hit play on the desktop app, the player shows up on the iPhone and iPad apps.  Does anyone have any ideas why the tracks aren’t available on the apps?