I have been thinking about this and I have a theory about what is happening. When you play TIDAL using a Naim streamer the authentication (your password and username) are exchanged with TIDAL and what normally happens is that the music continues to play. However if the authentication fails the music stops. It isn’t a different music file I don’t think. I have tried playing old standby pieces and I can’t see TIDAL recoding their whole library, it would be too much work.
What evidence do I have? Well, sometimes I use TIDAL on my mac so I can listen with headphones, then I start playing the Naim system and it cuts out. It’s because I am only licensed to use one stream and then second login is rejected. Then I go AHA and shut off the TIDAL app on the mac and it works again. The symptoms are very similar (although there is no guarantee that they are from the same cause, it does seem indicative) so maybe the authentication between the Naim firmware and the TIDAL server has changed and that is what has broken.