Ok, found the problem, it doesn't have anything to do with registration, activation, trial, antivirus, addon manager, couatl, etc.
There's a glitch in the updated installer (only the very latest one, and only the JFK one) that doesn't install a needed file if there wasn't a previous JFK installed on that system.
In your case, just run it again without uninstalling it, and it will work. If you already removed it, it should be enough to create an empty JFK folder under the fsdreamteam folder, under the main FSX folder and run the installer once.
We'll of course update the installer now.