pop-up window by button does not load content

Hello!

I’m using a child theme. When entering the site, the pop-up window by clicking the button works fine, but if you go down the page and update it, the form in the pop-up window is not loaded, the window is empty.
This happens with and without a stick menu.
I tried to delete all the changes made, it does not solve the problem.

Tell me, please, what can it be?

Thank you