Solved! Go to Solution.
Might have a solution to this problem, go to settings, sounds and notifications then app notifications. The list will take a while to populate if like me you have a zillion apps. Scroll to Spotify and uncheck or grey out hide sensitive content. That for me was blocking the player controls from coming up. Seems to be working now.
I suspect the latest security update from Google put that in place as I certainly never had all content hidden from Spotify and the last time it happened it took a soft reset of the phone to sort out. I think this might need to be watched as I suspect that this issue, might crop up again after a reset or another security update from Google...
Hope this helps.