Because.. you just replaced your hard drive and restored your computer to factory settings?
I'm sorry but you're not really giving us much to work on here
How is it not working anymore, what is the problem? Problems installing? Opening? Registering? Balance problem.
If you've recently wiped your computer, then all you should have to do is download Reason from this website and enter your ignition key, if it's not authorising then you have a problem with authorisation and should contact support who will be able to help you, otherwise what exactly is the problem?