But the menu is " GSX - Trial mode menu". and 3 trial airports listed there. Please help Thanks.
If the Addon Manager says it's Active, then it's Active so, it's possible you are mistakenly running P3D or another addon that starts with or launches P3D itself, in "Compatibility mode", like XP mode under Windows 7 or similar.
Check you don't run P3D into a “Compatibility” mode, like XP or Vista or Windows 7, under Windows 8. Turn off any compatibility modes for the Prepar3D.EXE, which is how it's installed by default.