@AJB_538 said:
Is there possibly another way here to force some sort of authentication reset or the like, on the Plex end?
There is this procedure, which signs the server out from the plex account.
https://support.plex.tv/hc/en-us/articles/204281528-Why-am-I-locked-out-of-Server-Settings-and-how-do-I-get-in-
While you are in the Preferences.xml, do set the SecureConnections preference to the value 2. This will disable them to make things easier for now.
