If you are experiencing Cubase 12 Pro or Nuendo 12 hanging on checking license screen, try this (Windows Users Only):
Go to 'settings' then Apps > Default Apps. Change your browser from any third party software like Brave browser, Mozilla, Chrome to Microsoft Edge doing that for every extensions like .htm, .html, HTTPs, http:, all link types, etc. Try opening Cubase again to verify if the problem is resolved.
I hope this guide help someone.