Yes, it's always the same, FSX doesn't even try to load it. Usually, when there's a problem like a missing .DLL, you would see the line with the loading attempt, and a message saying "Missing dependecies".
In your case, instead, it seems something is blocking the load before it happens, which usually is a symptom of the antivirus blocking it. Are you absolutely sure you don't have any antivirus running ?
To verify this, you can go to the Control Panel, under "Internet Options", look for the "Content" tab, there should be an "Authors" button, that will list the software authors that you trusted, and another tab with untrusted authors. If you see "Virtuali s.a.s", remove it from both tabs (especially if it's under untrusted), then:
- Uninstall the scenery, reply YES to the question "Do you want to remove the Addon Manager?" and "Do you want to remove the Couatl engine?" and reinstall it again. Pay attention if you get trust request from both Windows and FSX now.
I assume you are using the current version of the scenery installer ( or the Stand-Alone Addon Manager installer ) ? If not, download the Stand-Alone Addon Manager installer for FSX, and use that one as a reinstall, instead of the scenery, it's the same, but it's faster to do and it's a faster download too.