Cubase 7.5

Hello,please tell me!I bought cubase 7.5, installed on your computer,registered 8 ,seems to have done everything right,after 20 days ceased to open and run!who have come up against this and what can you suggest? :cry:

Well, you need activate the license (you are probably running Cubase as demo):

http://www.steinberg.net/en/support/productactivation.html