It gets weirder. I'm noticing differences in what tracks are available in the desktop app versus using Spotify in a web browser. Albums that aren't available in the app are showing in the browser. With some albums, all tracks show as available in the app but I get a message "can't play this song" when I click on them - but they're playable in the browser version. Some tracks that are greyed out as unavailable in my playlist are showing as available when I click through to the album - some not. I strongly suspect there's something gone badly wrong with Spotify's entire architecture, although strangely enough I don't see anyone else mentioning it online (like in the Spotify Help subreddit).