Have you checked the folders defined in your media-libaries? As far as I know there is a bug in the latest Multimedia-Station Update on QNAP directly interfering with plex.
Where have you stored your Media-Files? Hopefully not in the Multimedia-folder provided by default.
I can’t get access to the server, so i can’t define the media libraries. Was this what you meant?
I used to have several different folders for my media. But i’ve removed the previous install of Plex, in an attempt to “restart” the process. So now i’m just trying to gain access to the PMS. See below: