Child theme and change log

I make a lot of change to customize my coupon site and I see that I can’t create child theme using “Child Theme Configurator” plugin at here https://wordpress.org/plugins/child-theme-configurator/
It works with almost any theme except “Couponpress”. Do you known why?
I don’t want use the child theme of Premiumpress because I like the default theme, that’s why I want use third party plugin to create child theme for it so I can upgrade Couponpress without lost my customized.

Today, I see a new version of Couponpress 9.2.2 but I can’t find the change log of this theme
The change log I found here https://www.premiumpress.com/logs/changelog.txt is out dated

Please have a clear change log and tell me how to have a child theme and keep the default theme style

Thanks
Hai