Hello @HannaKidron , nice to hear from you.
A couple of weeks ago, settings for collaborative playlists were changed a bit to give playlist creators more choice on who can edit their playlists.
For you to be able to access and edit those playlists, you've to be added as collaborator(this is probably what you meant by co-creator).
The owner of the playlist has to send you a collaborators link which can be found in the menu inside the playlist.
If it's just a sharing link, you won't be able to edit the playlist.
Hope that's understandable.
But I'll be here if you have any questions or comments. Cheers.
Hey there you,
Yeah, you! 😁
Welcome - we're glad you joined the Spotify Community!
While you here, let's have a fun game…