The issue is, you do not have a "Now Showing" page. You have a site error 404 page that you added your Now Showing page content to. This is what is causing that issue. I recommend adding a new page, actually naming that page "Now Showing", putting the Now Showing content on that page, and linking your menu to that correctly created page. Then, go fix your site error 404 page back to what it was by default.