First of all: My AV is COMPLETELY disabled. In other words: No exclusion needed.
And that's a mistake. Never, ever, we suggested to "disable" anything. Antivirus are never really disabled, because their low-level windows service is always running and, I witnessed so many times the antivirus still interfering, even if it looked "disabled".
That's why not a single time we ever said to "disable" the antivirus but, instead, CONFIGURE it to add the whole Addon Manager folder to the antivirus EXCLUSIONS.
Second: couatl won't start automatically with MSFS (which is NOT my problem at all) because if it fails to autostart
It's not your problem but, it's a known MSFS bug, it doesn't start automatically for me either, and none of the programs in my EXE.XML starts automatically.
I just run it from it's original location as Admin.
That's what I find strange, and that's why ( according to your own report ) I said it was more likely the "access denied" was more likely a problem of having started two copies of the program at once, with the first one blocking access to the second because, running as Admin, you should always have access to the airport cache folder, that is %PROGRAMDATA%\Virtuali.
I'd say remove that folder and try again with the latest offline installer we released today but, I think you already tried that.