Rutter Christmas albums

That would be a question for Tidal.  Sonos is just a streamer/player, the content is provided by the content service.  You wouldn’t ask Samsung or LG why Rudolph the Red Nosed Reindeer isn’t available on Netflix, would you? 

I understand your reply, but it is a bit more complicated than this. There is a problem with Sonos playing Tidal tracks that actually exist. I contacted Tidal and they agree that the Rutter albums and tracks are fine. Everything is there in Tidal when I load their app. When I go to Sonos, tracks are ‘access denied’. About three weeks ago Sonos would not play Tidal at all. Sudenly Tidal reappeared. It seems to be a connection problem between Sonos and Tidal. I have re-authorised Tidal to no effect. I have screenshots of Tidal and Sonos but this thread does not seem to allow attachments.

It really isn’t complicated.  Tidal is responsible for their implementation in the Sonos app, through the Sonos supplied SMAPI interface.  So all access control, content display, etc., is the responsibility of Tidal.  It doesn’t matter if the Tidal app can list and play the tracks, the Tidal implementation in Sonos doesn’t access the same Tidal API as the Tidal app.  It is an entirely different implementation, but it is still the responsibility of Tidal to maintain.