It seems you called GSX too quickly before it was ready to run.
- choose "Restart Couatl and rebuild the airport cache" from the Couatl Settings menu
- don't do anything until the cache is rebuilt successfully
- in normal usage, don't try to call GSX before you see the green message on top saying "Airport cache loaded successfully"
- It might help to add the WHOLE simulator folder and every other folder in other drivers you might have sceneries on to the antivirus EXCLUSION. THis will speed up the cache rebuild process a lot, and lessen the chance of issues caused by the antivirus slowing or even blocking access to the scenery library.