Hi Brian,
It looks like a theme conflict.
Please could you do to Appearance > Editor, then select header.php on the right.
Find:
<?php if (has_nav_menu('header')): ?>
<nav class="nav-container group" id="nav-header">
<div class="nav-toggle"><i class="fa fa-bars"></i></div>
<div class="nav-text"><!-- put your mobile menu text here --></div>
<div class="nav-wrap container"><?php wp_nav_menu(array('theme_location'=>'header','menu_class'=>'nav container-inner group','container'=>'','menu_id' => '','fallback_cb'=> false)); ?></div>
</nav><!--/#nav-header-->
<?php endif; ?>
Replace with:
<?php if (has_nav_menu('header')): ?>
<?php wp_nav_menu(array('theme_location'=>'header','menu_class'=>'nav container-inner group','container'=>'','menu_id' => '','fallback_cb'=> false)); ?>
<?php endif; ?>
That should let the default Max Mega Menu responsive menu show up instead of the theme one.
Regards
Tom