I think you have been replied to on Discord.
For other reading this, the problem was caused by one of the two GSX packages in the Community folder being a real folder instead of a symbolic link, possibly related to the move of the whole simulator.
The two GSX packages in the Community folder MUST be shortcuts, not real folder, which is how they are normally installed. Removing the package that wasn't a shortcut and pressing "Relink" in the FSDT Installer has fixed the problem.