Can't Activate Product

Hi all

1) I managed to activate product on computers with Windows 10 and 7. On Windows 8.1 I couldn't do it.

2) When I write down incorrect e-mail and password Bitdefender does say that it's incorrecet.

3) When I wrie down correct e-mail and password and I press "Log in", I got endless doing sth.

Any thougths how to resolve this problem?

Best regards