Hi,
Thanks for reaching out.
I have checked your backend. You are using Helix3 and Helix Ultimate framework at the same time. Since they are different in so many areas including module position,layout, etc, they can conflict when using together. As the kidzy template is based on the Helix3 framework, I have disabled the Helix Ultimate framework instances.
https://share.cleanshot.com/DWlPfF5K
Now your changes reflects. You may have adjust the logo height and appearance according to the logo image size and your header height.
Please check now and let me know.
Best regards