Drupal 7: Main menu not displaying child elements

In my main menu, I have primary links and child links. The primary links are printing just fine. However, when I make a child element (by either dragging it to the right or selecting a p开发者_如何学运维arent link), they aren't displayed in the menu at all. I can create a new menu, and the child elements display correctly. I also ensured that 'Show as Expanded' was selected. Are child 'Main Menu' elements not suppose to show up?

All levels/childs of the menu stucture should be set in one menu tree (Main Menu in this case).

Now go to admin/structure/menu/settings and set your Main Menu to both Source for the Main links and Source for the Secondary links.

Which theme are you using? If you using Bartik then that is your problem as the Bartik theme doesn't support drop down menus. See here http://drupal.org/node/1508652 The link includes a work-around