The Plex Pass is connected to your plex.tv user account, and not to your computer.
I can see that the account which you are using to post in this here forum has a Plex Pass attached.
So I suggest using this one with your Plex server and all your plex clients as well.
To find out the email address of this account, simply click on this link: https://app.plex.tv/desktop/#!/settings/account
If your server was accidentally connected to a different account, you must sever this connection first. Then you can re-claim the server with the right plex.tv account.
To sever the connection with a plex account, you need to close the server and then edit the registry.
If you are afraid to edit the Windows Registry directly, you can use methods 2 or 2.2 described in this post: You need to reclaim your server, but don't dare to touch the Windows Registry
Is your server machine still running on Windows 7 or did you upgrade to Windows 10 / 11?
