Mobile Menu Doesn't Work in Child Theme

I am using the Myth Theme and created a Child Theme the old-fashioned way, with a custom style.css file using @import for the parent CSS. The Mobile Menu works on the Parent Theme, but in the Child Theme, when you click on “Menu” the background changes color to show it’s activated, but the Mobile Menu just does not appear. Tested on Chrome for Android, Safari on iOS, and Safari on Mac.