Another Mobile Menu Problem

Sometime within the past few months, following some sort/set of updates, my mobile menu stopped working for our website, http://www.honors.olemiss.edu. Based on other posts, I’ve stepped through disabling plugins to see if one them has affected it, and none of them have changed the behavior. I see no errors in the JS Console of Dev Tools, but can’t call the function to show_mobile_menu directly from there either.

Any advice or suggestions on resolving this would be appreciated.