Spotify has arbitrarily decided to remove Apps 4 Automotive Android functionality in their current versions of software. I've been a Spotify subscriber for a long time and this is just another in a long list of backwards decisions by them to remove useful features. You can however, still get it to work if you stick to an older version of the Spotify software. After it stopped working for me, I downgraded my app to ver. 8.5.60.1013 and normal functionality has been working pretty consistently (there are still occasional glitches). It's a bit of a pain to have to remember to never update the app when doing other app updates - you will have to turn off Auto-update or else constantly have to re-install the old version, but it least it's working.
You can read more about it in this article:
https://www.bmwblog.com/2020/08/17/a...a%20statement.