Menu button does not expand hidden mobile menu.

I have installed WP Opulus but now see that the top right button which shows when you are using a mobile (or narrow screen) does not display the menu. In fact it seems to do nothing at all, despite the CSS around it appearing to be exactly the same as the demo.

Is there something wrong with my JQuery / Javascript?

This is the church website where I an having the problems: http://test1.christchurchtunbridgewells.org

Thanks