I have accordions installed in my WP site.
Inside an accordions content, i try to add an iframe to show a special html page.
There is a specila button a the top of the accordions edit page
it's called "Add Advanced iFrame", but there is no response of the site when i click on it.
Welcome to our forum.
I just checked your admin, can see there is js error from “advanced-iframe” plugin. please see the screenshot, you should contact with plugin dev. I am not sure if this plugin has support for custom post types like accordions.