menu items not showing up

Hi, i just start using the presentation version of the theme but the menu items that i placed in my new menu are not showing up even though i create the menu, place the items in the new menu and select and save the location of the menu (main). the menu items are not showing up in the menu bar. instead i see the following message; please attach a menu to this menu location in appearance > menu.

any idea what could be causing this problem?