There are some known issues registering Windows 8 Enterprise with the correct product key.  For many people they are getting DNS errors when trying to register.  Here is how to register Windows 8(or any version of windows) from the command prompt when you are unable to do it normally.

1. Open command prompt as Admin (right click it, run as admin)
2. Type –‘ SLUI.EXE 3 ‘
3. This opens the “Activate over the internet” windows.
4. Enter activation Key
5. Click on activate and it should give you a message that windows has been successfully updated.

Hope that helps, remember you can also activate over the phone, but I prefer internet unless there isn’t a connection to be obtained.