This site is being deprecated.
Please see the official X‑Plane Support page for help.
I'm just another simmer in the UK, but have you tried downloading X-Plane 11 straight from their website, assuming you have high speed access to the web?
If you already have the demo version on your PC, then presumably this was downloaded from the web and if so, you should be able to activate to the full version with your DVD Licence Key.
This site is no longer being actively maintained.