Mobile Menu css problem in catch responsive theme

I seem to have caused a problem with my mobile menu. In a phone sized view it works perfectly, but the intermediate view of a tablet loads the hamburger menu, the menu opens, but there is no content from the actual menu. It just looks like a blank panel that slides open. Any change a kind soul is out there that can review this; i have been staring at it for days and cannot find what I did. the site is https:isc2rduchapter.org Any help would be greatly appreciated