Its like the file wasnt opening on installation.I copied and pasted a COuatl.
It was probably killed by the antivirus. What created the problem was, you haven't properly turned off the antivirus realtime protection during the installation.
It's not enough to configure the antivirus to ignore Couatl.exe when it's located in the FSX folder because it will still be blocked when it's inside the temporary folder, which is were the installer uncompress the files, before being copied to the FSX folder.
That's why, the antivirus believes the file is a threat, it needs to stay off during the installation.