no trace of the old KJFK version anymore as it was properly uninstalled when I bought the new V2
Uninstalling a scenery will not remove the activation. That's of course intentional and it makes sense: this way, you don't have to reactivate if you *just* want to uninstall/reinstall a scenery, for any reason. Even uninstalling FSX entirely, will not remove your activation.
The addon-manager shows KJFK V2 PROPERLY INSTALLED AND REGISTERED (it also works flawlessly) and the old KJFK as "not installed"
That's exactly how it's supposed to be.
Nevertheless this pop-up window claims to have found an "installed, but not active" version of JFK
Perhaps the message is a bit misleading: it hasn't found an installed scenery, it found a JFK Serial Number in your registry.
I have checked all possible entries in the registry and in the whole FSX installation, I do not find ANY trace of the old KJFK
Sure there is one, here:
HKEY_CURRENT_USER\Software\Fsdreamteam\JFK
If you remove that folder, the message will go away.
Activation of course is not possible either and does return an error, as there is definitely no KJFK V1 installed anymore
Activation IS possible, instead. Fact that JFK is installed or not as a scenery, doesn't have any relationship with the ability to activate it. If your JFK Serial is valid, it WILL be activated.
However, I've checked your order, and it the issue is that the Serial still in your registry belongs to an order you have been refunded for, because you purchased JFK V1 twice by mistake, instead of purchasing JFK V2 with the Coupon. Since the order was refunded, it can't pass the activation anymore, which is logical.
Just remove the above folder from the registry, and the message will go away.