Playlist? And Subscribe?

[TheDreadPirate]

Starting in 10.9, playlists made in Jellyfin are tied to the creator. If you've reinstalled Jellyfin then your user ID changed and you are no longer considered the owner. The owner ID is written in the XML playlist files that Jellyfin creates. You can try making a copy of the playlist and changing the owner ID and then adding the playlist back into Jellyfin.

A simple way to find your userID is to go to Dashboard > Users and click on your user. In the browser's address bar, part of the URL will be your userID.