It’s the exact symptom for the issue I had described above.
If Plex thinks you’re not the owner of the server or you got yourself locked out, it’ll give you a “naked” web app but none of the server’s “local” capabilities (e.g. none of your libraries, media or server config).
As for being locked out… if you indeed got yourself locked out:
I’m not exactly sure if/how you can access the preferences.xml file on a WD PR2100. On other NAS platforms you can SSH on the device to access its internal file system and access those paths
