Warp Framework (YooTheme)

This theme manipulates the output of the wp_nav_menu function, completely removing control from UberMenu. To use UberMenu, you’ll need to manually integrate UberMenu to replace the theme’s menu system.

In layouts/theme.php, you’ll find this code around line 73ish (this may vary from theme to theme)

<?php if ($this['widgets']->count('menu')) : ?>
	<?php echo $this['widgets']->render('menu'); ?>
<?php endif; ?>

Use manual integration here to replace it with UberMenu

<?php if( function_exists( 'ubermenu' ) ): ?>
	<?php ubermenu( 'main' , array( 'theme_location' => 'main_menu' ) ); ?>
<?php elseif ($this['widgets']->count('menu')) : ?>
	<?php echo $this['widgets']->render('menu'); ?>
<?php endif; ?>

Ideally, this would be done in a child theme, though I’m not sure if this theme supports child themes, as the theme uses non-standard templating practices.