SOLUTION TO INVALID REGISTRATION NUMBER.
OK, After registering for a serial number by using my Opera browser as Chrome wouldn’t work, I recieved the confirmation email. I confirmed my email address and ran the installer. I received the serial in a second email and entered it into the program. It failed as invalid. After trying various things, I discovered you have to enter your email as your name AND ALSO as your business name. Once I did this, the program was registered.
Phew! I hope this helps.