Thank you for reaching out here in the Community!
By saying that you cannot start the playlist again you got us thinking that a corrupted cached files might be interfering with the app's performance on your device. We'd recommend to clear cached files on it following the steps in this article.
We can also suggest that you check your phone's battery settings and make sure that Spotify is set as an exception if you're using the battery optimization option.
In case you still experience the issue, could you let us know if it happens on all your playlists and if it persists when you're using the app on a different device?
Let us know how it goes.
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