Toggle navigation button not functional

When I view my website on my phone (or on a browser that is set to a narrow enough width that the nav menu is replaced by the toggle navigation button), the button to toggle the nav is non-functional unless I scroll down to where the nav bar is pinned to the top of the page. I am using the Sticky Menu plugin. If I disable the plugin, the nav toggle button doesn't work at all (since the nav bar is never pinned to the top of the page).