You should always try to keep that data on an internal drive.
Did you complete the move of the files, then changed the data folder path in Plex and only then re-started the Plex Media Server?
If the underlying issue is that you’re running out of space on a small boot drive, for instance, then the easiest solution is often simply to relocate the Plex Media Server data directory.
Tip! : When relocating the data directory, you should make sure you do so to an internal drive on your computer (hard drive or SSD). Moving to a network location can result in poor, unexpected, or even completely broken behavior.
Windows
For Windows installations, you can make use of the The Path where Local Application Data is Stored general server setting. Refer to information about that setting for details.
You can set the location where your Plex Media Server data directory is located. This is the path to the directory containing the Plex Media Server folder.
Note : Altering this setting will not move the data for you. You will need to ensure the data is in the desired location yourself.
Warning! : You should not specify a location that resides on a network share/disk.
Yes. I stopped the service and shut down plex. Moved the folder. Once moved I restarted plex and moved the location in plex advanced settings. Then I restarted the computer.
Plex wont start at all now.
I moved it off my main drive because I only have 1 internal drive which is 250G. Apparently my plex folder is 175G, that leaves not much space for anything once windows is on there too.