Here is my opinion. Your issue is two-fold:
You have moved the Plex data folder to a ‘naked’ drive letter, without pointing it to a folder.
Step one:
Move your plex data from G:\Plex Media Server\ to G:\Plex\Plex Media Server\ using this procedure: Moving Metadata on Windows - #3 by OttoKerner
Step two:
Edit the Windows registry as described in this post (make sure all Plex processes and system services are stopped beforehand)
