Confusion

[Doc_Z]

I had GSX on my machine and it was working fine.  I bought and downloaded GSX Level 2.  I had some trouble getting it to accept the serial number (it would just close, but eventually I got the number in.)  The add on manager said both GSX and Level 2 were active, but I could not open the airport configuration page.  I uninstalled version 2.xxx with the Windows installer.  GSX is not present on my add-on list in the sim, but the add on manager still stays both are active.  Do I need to find and reinstall the original GSX? Or does the new one take care of it?

[virtuali]

GSX is not present on my add-on list in the sim

If you mean the addons listed in the "Options->Addons" menu in Prepar3D, you are not supposed to see GSX there. Only the Addon Manager.

If, instead, you mean GSX is missing from the "Addons" menu under the top bar of the sim, then you have a problem. Is this the case ?

[Doc_Z]

I reinstalled using the 2.5.0.5 installer and GSX shows in the add-ons list as it should.  If I go to the Addon Manager, it says Level 2 is in Trial.  I click on Register Serial and either nothing happens or the box comes up, but I can't type or insert anything in it.

[virtuali]

I click on Register Serial and either nothing happens or the box comes up, but I can't type or insert anything in it.

It seems you have another addon that is "stealing" the focus of the registration dialog, by continuing to force itself into the foreground.

First, be sure you run the simulator in Windowed mode. Also, DO NOT start the simulator from another addon, but start is only from its own icon. If that still doesn't work, disable all the other addons that might do this, at least while activating.