Resolved – Turns out my page was not using <?php wp_footer(); ?> in other languages somehow, changed that now. The javascript was not being used.
Please remove the links to the websites in the issue above, thank you!
Resolved.
The problem was that the mega menu on the active theme site got a different class than the mega menu on the other (the front page). The front page got “top-menu” as class and the active theme pages got “primary” as class.
This made the copied CSS not find the menu.
You may remove the links, the problem is no longer visible.
