What have you already tried:
I’ve checked and it’s an issue accross all browsers. I’ve tried both adding a new menu element and creating a new menu in the Menu Manager, and neither has had any effect. I’ve also checked and there’s nothing overlapping the menu or anything like that.
Additional information:
I’m using the first of the standard ‘Horizontal Menus’ options in the element tab
After exploring the site (looks great by the way!) it appears the Header Section is set to hide Overflow Content, this causes the ‘More’ option of the Menu to be hidden, as this window overflows in the Section below the Header, I have created a quick Video which should help