Mobile Menu doesn't show when not logged in as admin

Hello,

I have a theme that I've been using that's based off of _s. I use it for my class website. Today I noticed that my students can't see the top menu bar when on mobile devices. It seems to work just fine for me when I'm logged in as an admin, but when I'm logged out or logged in as a student (subscriber) the height of the menu bar is wrong, the menu-toggle hamberger icon doesn't show up and students can't access the menu. I was hoping you could give it a second set of eyes to help me figure out this problem.

http://kickmymath.com