Responsive/Mobile menu not working

Hi,

I have a question concerning the mobile menu as it is not working on Safari for Iphone (I haven’t checked on other mobile devices). When I tap the menu button with the 3 horizontal bars, the button changes from transparant to light grey and that’s it. No menu appears.

I’ve created a child theme and have made several changes to the header and to the position and color of the menu block. I don’t think the issue is necessarily with the child theme though, because when I activate the original Matheson theme the behaviour is exactly the same.

The website is https://www.susannesluytermanvanloo.nl. Any help is much appreciated!