Hi SSS,
Once you get the pop up, click on license and then login with your Adobe id (email id registered with Adobe id) and password.
That should resolve the problem. If doesn't , uninstall Acrobat using Acrobat cleaner: http://labs.adobe.com/downloads/acrobatcleaner.html
Reinstall Acrobat and register with Adobe id and password. Make sure your computer is properly connected with Internet, without proxy.
Regards,
Ajlan Huda.