Is Plex Media Server running on the WD NAS or on your Mac?
My reply was based on PMS running on the NAS. Apologies if I misunderstood.
If PMS is running on the WD NAS, then the User Credential Reset utility does work (see this post in the thread). The script runs on the NAS, not on the Mac. It does not require anything but a terminal session on the Mac.
If PMS is running on a Mac (or other system) and cannot access media on the NAS then that is a SMB/NFS file sharing issue between the NAS and the Mac. Your Plex account password is not involved.
If you need to re-claim a Plex server running on a Mac, see Why am I locked out of Server Settings and how do I get in?. After issuing the terminal commands, reboot the Mac, start Plex Media Server, and see if you can login and claim the server.
I do not have a WD NAS (I’ve a Synology). That written, I’d hold off on using the nuclear option as long as possible. As you mention, it will take a week to get back up and running.
