Hello,
Since this is a free template we didn't build in the register class which is needed for s5box to function. You would need to open up the index.php file and look for:
<a id="s5_register" href="/component/users/?view=registration"> <?php echo $s5_register;?> </a>
Then replace it with the following:
<a id="s5_register" class="s5box_register">
<?php echo $s5_register;?>
</a>