Purchase a from the FSDT store to activate all airports. To help you get the best experience, Explain the difference between GSX and GSX Pro ?
If you want enhanced ground services without the cost of GSX Pro, the MSFS community offers excellent free tools:
When you launch MSFS, GSX Pro checks your license against FSDreamTeam’s servers. If the server doesn't see a verified purchase ID linked to your hardware ID, the software enters "Demo Mode" or simply refuses to load the 3D models.