Hi Roland,
Thanks for reaching out!
I check your website and I found out that there’s a conflict with your theme JS that preventing the Cornerstone plugin to load. Cornerstone is powered partly by JS. If there are JS issues with the theme, Cornerstone, like other builders, will not work.
You need to remove or find a workaround with the conflicting JS from the theme. Regretfully, we cannot fix the issue of your theme because it is outside the scope of our theme support.
On the other hand, the reason why I can tell that it is a theme conflict is that when I tried to activate the default theme like ( twenty twenty-one) the builder works fine.
Hope that helps and thank you for understanding.