The first step would be having GSX read the correct AFCAD file. First, be sure the addon AFCAD it's on an higher layer than the default one.
It's possible the AFCAD has been rejected for some reason.
- Enable Logging in the Troubleshooting section of the GSX Settings page
- Choose the "Restart and Rebuild the airport cache" option from the Couatl menu
- Exit from the sim and check your Couatl.LOG file in the %APPDATA%\Virtuali folder. It should tell you why you .BGL has been rejected, assuming it WAS rejected, and it wasn't, for example, a simple case of another scenery in conflict.