from another Post:
Good Evening,
If you are using FSDT scenery purchased through the MS Marketplace and you are attempting to download the new GSX update. I identified a workaround that will allow you to download the update. This update will fail if you are using FSDT scenery purchased in the marketplace only and found in your "Official" folder.
1) Before running Installer or Live Update, navigate to your local/packages folder. From there you will have two choices either your community folder or the official folder.
2) Select the "Official" folder. Navigate and find your FSDT airports. Then cut them from your official folder and move them to your desktop or other location outside of the "Official" folder. Make sure there are no other FSDT sceneries in the Official folder.
3) Run the Live Updater or Installer and update GSX as normal it should work as intended.
4) When the update is complete, paste your FSDT sceneries back into your "Official" folder.
5) Boot into MSFS and enjoy the update.
I hope this will help the developer identify where the issue is, because there is one and it's with their sceneries when attempting to download the GSX config files for those airports.