I bought a GSX now and it works for me only three airports ... how to open it to all the airports?
You said you bought it, but you don't say if you have *activated* it.
- Activate it as explained on your purchase receipt (using the "Register Serial" option in the Addon Manager menu )
- Restart FSX
Assuming you activated it correctly, and the Addon Manager would report it as "Active" in the next FSX run, if it STILL shows you the Trial airport, it's likely because you are running FSX into “Compatibility” mode, which is not how FSX should run (reduces performances, and create lots of other issue) and it’s not how FSX is installed by default.
Check you don't run FSX into a “Compatibility” mode, like XP or Vista or Windows 7, under Windows 8. Turn off any compatibility modes for the FSX.EXE, which is how FSX is installed by default.