If you can’t add or move playlists between folders as expected you might need to run a clean reinstall of the Spotify app on the affected device. This will remove any cache data that could be causing the issue.
In case this persists, check if any battery optimization settings or data cleaning apps run active on your mobile device and disable these. Such features can often prevent the app from operating at full capacity. We also suggest checking the app settings and making sure all permissions are enabled for Spotify.
Another thing you can try is checking the hosts file on your PC. If you find any entries including “spotify” make sure you delete them.