Additional levels of the menus must be styled using CSS in your stylesheet before they will show.

If they are styled, verify that there isn't any incorrect javascript running on the page. In particular, check all javascript running in Formatted Text & Images parts, Unformatted Text parts, or in the Site Tracking area under Administration, Sites & Settings.

Our Website Introduction documentation covers the basics of layouts, stylesheets, templates and pages: https://www.blackbaud.com/files/support/guides/bbnc/BBNCWebsiteDesign.html