I’ve had this issue for years and have posted here about it a few times.
Songs in my playlists that are from original motion soundtracks don’t always play. Most of time they won’t play at all, other times I have to restart the app to get them to play.
I pay for this service to work but it’s been years since I can confidently listen to certain playlists. I usually just switch to Apple Music which is looking like the way to go.