Parallels 11 activation on OS X 10.13.6 fails (Check your Internet connection)

Dear @Avinash Bundhoo, I'm experiencing the same problem as everyone else on this forum. Had to replace the motherboard on my Mac, and after trying to reinstall Parallels, I get the "can't connect to internet" error message when trying to activate the license key. Used to work just fine before. Tried all the recommended troubleshooting tips, but no luck I'm afraid. Are you able to help please? Many thanks, ed.