Cubase quit unexpectedly on OS X El Capitan

I’ve just bought Cubase Artist 8, I installed everything and entered the license key, registered etc…

When I went to open the program it either comes up saying Cubase quit unexpectedly or asking me to put in the license key again, to which it then pops up saying that its already registered elsewhere.

Hope someone can help!

I can post the problem report if it will help.