I've had to uninstall FSX- it was getting scrappy, installation of a certain product made all my menus look greyed out, FSUIPC was causing issues with a couple of add on's and it wasn't well at all.
SO, I've done a full uninstall using a few sources to make this effective then tried to reinstall.
It does so, but at no point does it ask for the licence key. It then runs 30 mins and shuts down saying something like "hey, thanks for trying now you need to activate".
If it'd give me the opportunity- I would.

I've tried 3 un/reinstalls. Same result.
Any ideas???
Thanks,
Paul