GSX obviously work with all P3D 2.5x versions. If a specific version is not supported, you would see a clear error message when starting about the version not being recognized.
Since you have the Addon Manager menu, but not the Couatl menu, the most likely cause is the antivirus blocking it. As discussed in all threads about missing menus, reinstalling with the antivirus disabled is NOT enough, you must do the following:
- Download and install with the antivirus ENTIRELY DISABLED
- BEFORE starting FSX, configure the antivirus to exclude the following files from scanning:
YourP3DFolder\bglmanx.dll
YourP3DFolder\fsdreamteam\Couatl\couatl.exe
YourP3DFolder it's usually C:\Program Files\Lockheed Martin\Prepar3d v2, if you installed it in the default folder.
- Be sure you exclude files for the real-time protection, not just for manual scanning (Norton has two separate settings, for example)