Why did the mega menu in my store stop working?

I’m testing out the “Dawn” theme in my Shopify store. When I first set it up, everything worked fine. Then, suddenly, the “Mega Menu” stopped working. It shows in the editor as if it’s there, but when I load the page up in a separate window, it only shows the traditional drop-down menu. I’ve spent hours, upon hours searching for something that would help, and there’s nothing. Is this part of a 2.0 issue, or has this always been a problem with Shopify?

@Fresche

Could you provide me store URL? I should be able to answer your question.

Yours faithfully!