10.2 Tokyo downgrade to Delphi XE7

Hello, I have purchased licence for Delphi 10.2.1 Tokyo, I had registered it in https://reg.codegear.com/srs6/activation.do and downloaded *.txt file, then installed it on my PC and all goes fine.

But now I want to install Delphi XE7 with serial from Delphi 10.2.1 Tokyo, but when I get registration window in install process, and trying to enter Delphi 10.2.1 Tokyo serial number i got error => 'Serial number is incorect' or 'Licence file is incorect'...

So what I need to register my Delphi XE7 copy?