but after loading ca. 93% fsx crashes and I get a message: "Failed to read from file", clicking OK (the only opportunity) FSX restarts
. I downloaded the latest version of Add-on Manager but with no result. I think maybe it is the missing add-on manager and couatl engine that is causing FSX to crash.
That's exactly the opposite: missing Addon Manager/Couatl can't obviously crash FSX. If you don't see their menus, it means they haven't been loaded by FSX, so they can't possibly make it crash.
You are probably getting it backward: it's your FSX crash, which is caused by something entirely different, which is *causing* the Addon Manager/Couatl not loading.
If you Google "fsx crash failed to read from file", you can see there are multiple reasons for this, none of them of course being related in any way to the Addon Manager, it's your FSX install that is surely missing something and/or has corrupted files.
Since just a few days ago, you said:
Did what you said, and it works fine now, both airports
It's fairly obvious that the Addon Manager works on your system, but something ELSE happened in the meantime, that is has AFFECTED it, so is not loading anymore and it also causing FSX to crash.
I repeat and confirm: if you don't see the Addon Manager/Couatl menus, they haven't been loaded by FSX so, obviously, they can't be the cause of the crash, they are the victims instead...