First, may I make a suggestion? Your site is set to be 1575 pixels wide (this isn’t Twenty Eleven’s default width, so I’m assuming you set it that way). My main computer has a very big monitor, so it showed up fine.
But my other computer has a lower resolution (1600 pixels wide), and including the margins on your site, the total width is 1635 pixels, meaning I have to scroll horizontally to see the whole page.
Here are screen size statistics. 25% of users have a width of 1366px, so you want to be at least that narrow to accommodate them.
…
Anyway, can you double-check and make sure you’ve got your custom menu set up to display? In the Menu screen, there’s a box on the left that says Theme Locations, and it has to be set up there.
Assuming you’ve done that, could you go into your header.php
file and copy-paste the code for the nav bar? It starts with <nav id="access" role="navigation">
and ends at </nav><!-- #access -->
Here’s the code from my own copy of Twenty Eleven, so we can compare and see if/where they differ:
<nav id="access" role="navigation">
<h3 class="assistive-text"><?php _e( 'Main menu', 'twentyeleven' ); ?></h3>
<?php /* Allow screen readers / text browsers to skip the navigation menu and get right to the good stuff. */ ?>
<div class="skip-link"><a class="assistive-text" href="#content" title="<?php esc_attr_e( 'Skip to primary content', 'twentyeleven' ); ?>"><?php _e( 'Skip to primary content', 'twentyeleven' ); ?></a></div>
<div class="skip-link"><a class="assistive-text" href="#secondary" title="<?php esc_attr_e( 'Skip to secondary content', 'twentyeleven' ); ?>"><?php _e( 'Skip to secondary content', 'twentyeleven' ); ?></a></div>
<?php /* Our navigation menu. If one isn't filled out, wp_nav_menu falls back to wp_page_menu. The menu assigned to the primary location is the one used. If one isn't assigned, the menu with the lowest ID is used. */ ?>
<?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>
</nav><!-- #access -->