Hi Destrega,
First, are you entering the right key? If you installed both the game and NH in a row, the order of keys has to be right..
If it is;
Have you double checked and made sure you didn't make any typing errors?
That key should be unique and valid, if it worked before, it should work now. So perhaps a typo?
If you're sure that you got it all right, you can PM it to me, after which I'll try to get help from vstep for you.
Regards,
Fred