I can't register my serial number

If you download and install the latest version of Professional from here: -  https://www.betangel.com/download?product=BetAngelPro

It can automatically register purchases for you.

When you log into the front screen, it'll first prompt you to verify your e-mail address, and then having gone through the e-mail verification process, it will be able to lookup your purchased serial number(s) from that point onwards. No need to enter another serial number!