The download stops half way through the "copy local Coutal updater executable" and just freezes.
If it doesn't fix after a Windows restart, it looks like an antivirus bug, which has mistakenly detected the program as a threat, and is blocking it from being installed.
- Download and install with the antivirus ENTIRELY DISABLED
- BEFORE launching FSX, configure the antivirus to exclude the following files from scanning:
YourFSXFolder\bglmanx.dll
YourFSXFolder\fsdreamteam\Couatl\Couatl.exe
- Now you can turn your Antivirus on, and launch FSX