Hi @Snaggletooth
Thanks for your post!
Music services do occasionally remove tracks from availability - usually due to licensing concerns. It’s possible that this is what’s happening, but I wouldn’t expect you to then be able to play the same track in the Spotify app. Spotify does maintain separate servers for third-party access (such as Sonos) though, so it could be the servers aren’t at parity.
However, I recommend you get in touch with our technical support team who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports. You certainly shouldn’t need to reauthorise Spotify regularly at all.
I hope this helps.
"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein