When I have to download KMEM to activate it, what comes up is the default scenery.
If you see the default scenery (do you see the default airport or you see an empty field ?), the problem doesn't have anythign to do with the activation.
If you lose the activation for any reason or you still haven't activated the scenery, it will not "disappear", it will run in TRIAL MODE, meaning you will see the whole airport for 5-6 minutes per session and THEN it will disappear, but it will reappear again if you restart the sim. There's no expiration for the Trial.
So, if you really have the default scenery, the only explanation is:
- You haven't installed KMEM, or it was installed it in the wrong folder, most likely if you use FSX:SE because you removed FSX after installing FSX:SE and the FSX registry keys are now wrong.
First, be sure you use the CURRENT installer for KMEM, not an older installer you might have downloaded in the past, since the current installer is more capable to deal with wrong registry keys when FSX+FS:SE are involved.