“Add Item” Button not Working (listing_id not found)

Hello,

When I try to add or edit an “Explore Event Listings” plugin, and I try to add a listing category via the “Add Item” button, nothing happens. When I look at my javascript console, I see an error that says “listing_id” not found.

A while back, I editing all of the listing categories, but at that time, I was able to work around to get the new categories to show up.

Can you help me determine the problem and solution? Thank you.