And still only addon-mangager in Add-ons list, guys please help, and do something about this hell, so many customers have problems with it, so please please please fix this, this is so annoying, and makes me so angry...
There's nothing to "fix". There hasn't been a single case ever reported, that a failure to even *start* the program has anything to do with it. ALL reported cases of a failure to START, are always the result of some external interference, and in 99% of the cases is the antivirus.
This, based on your report of Couatl not even starting.
If, instead, is not really "not starting", but it starts and then it crashes after a while, then it might be an entirely different issue. Again, always caused by external factors that we cannot fix on our side, just different ones.
To verify if Couatl just doesn't start, or it crashes, try to keep the Task Manager open while FSX is starting, and pay attention if the Couatl.exe process appears, even for a brief moment.
If it doesn't appear, and you are sure you authorized it and not un-trusted it, than it's almost invariably the antivirus, not properly stopped when installing, or not properly configured before starting FSX, or a combinations of the two.
In, instead, is starting and then crashing, we can have some troubleshooting options in Couatl to verify the issue.
The obvious point is: if Couatl is not even starting, because something else is blocking it, there's just nothing we can "fix" on it, because OUR code hasn't even STARTED. That's the whole point of security software: they are blocking a program BEFORE it got even a chance to run its first line of code. If they didn't do it, they wouldn't be very effective, and if we could "defend" ourselves against a security program that is mistakenly blocking our program by doing "something", that would defy the purpose of having a security program in the first place. Unfortunately, they ARE very good at blocking programs but the issue is, they are SO good, that they block even legitimate software in the process.