Then my first assumption is that the session token is not being correctly stored in kwallet. It can't restore the session after kwallet is closed.
You can open kwallet manager, and delete the wallet. This will prompt your system to re-create it next time you go to use something that needs it (wifi, nextcloud).
This will allow you to essentially reset the default wallet.
The typical settings for it are "blowfish" encryption with either a blank password (which encrypts nothing, but allows the wallet to always open reliably) or using the same password as your user (which allows the wallet to decrypt automatically upon login).
There is also an actual Jellyfin Rewind though you do need to have been using the playback reporting plugin.
This years isn't done yet.