GSX is supposed to recognize you installed a new airport automatically, and should refresh its airport cache on the first startup after the installation of a new scenery.
Just to be sure it did, try to force a cache refresh from the Couatl Settings menu, with the "Restart and Rebuild Airport cache" command, then go again in the parking customization screen, to check if the AFCAD in use now it's correct.
If it's not, there might be a number or reasons why it might have been rejected. In this case, it's best to enable Logging in the Troubleshooting section of the GSX Settings, then "Restart and Rebuild Airport cache" again.
After waiting for the cache regeneration to be done, exit the sim, and check the Couatl.LOG file which has been created in the %APPDATA%\Virtuali folder, and hopefully it will tell something about why that scenery wasn't accepted.