About the issue for gnome extension - Blur my Shell

I want to change my application windows like this video below.
Youtube - " GNOME 40, Blur Effect on Application Windows (with Shell Extension)"

But when I done, and my application windows become to totally transparent. Why?
Please help me. Thank you.

You won’t be able to merge the pull request mentioned in the video as it’s still a work in progress and has conflicting files. What exactly did you do?