Instructions:
You must use the 'menu' argument along with the slug you assigned to the custom menu in functions.php
and NOT the 'theme-location' arg, or it will not work!!
<?php
wp_nav_menu(array(
'container_class' => 'navbar-collapse collapse',
'items_wrap' => '<ul class="nav navbar-nav">%3$s</ul>',
'menu' => 'primary-menu',
) );
?>
On one line:
<?php wp_nav_menu(array( 'container_class' => 'navbar-collapse collapse', 'items_wrap' => '<ul class="nav navbar-nav">%3$s</ul>', 'menu' => 'primary-menu') ); ?>
Output:
<div class="navbar-collapse collapse">
<ul class="nav navbar-nav">
<li ... ></li>
</ul>
</div>