Unable to register parallels desktop

Hi all
I am using parallels desktop 7 for Mac but unfortunately I am not able to register a copy of my parallels desktop.
When I start the registration, I get an error on my screen. the screenshot of the error is as follows:

Unable to register Parallels Desktop.
Check your internet connection and try again. If the problem persists, follow this link to register your copy of Parallels desktop.
Can anyone please help me out of this problem? I am stuck. Any helpful advice will be most appreciated. Looking forward to your comments.
Kindest regards.
