Error when using Plex Media Servre with Mac

I was using Plex Media Server with my Mac at home and one time I was trying out different skins.
I then launched Plex when I got this error message, see screenshot below.
I tried searching the web so far, but I couldn’t find any solution. I tried looking for the xml file, but I couldn’t find it also.
Can anyone give advice on what to do next? I can’t use Plex right now.

Fatal Error
/Network/Servers/
bezzelewisserver.privatesky.studio/Volumes/SkyHD/
NetUsers/willeyeam/Library/Application Support/
Plex/guisettings.xml, Line 0
Failed to open file
