JSSOR "Error: prototype of 'thumbnavigator' not defined" - jssor

Question

The full JavaScript error is:
Timestamp: 6/4/2015 8:52:37 AM
Error: Error: prototype of 'thumbnavigator' not defined.
Source File: http://webanautics.com/invoice/slider-master/js/jssor.js
Line: 69
I have read the other answers to the same question, but the answers don't work for my particular code.
I'm using the tabs-slider example, enter link description here
My Slides Container looks like this:
<!-- Slides Container -->
<div u="slides" style="cursor: move; position: absolute; left: 0px; top: 29px; width: 900px; height: 600px; border: 1px solid gray; -webkit-filter: blur(0px); background-color: #fff; overflow: hidden;">
<div>
<div style="margin: 10px; overflow: hidden; color: #000;">
<?php $week = -1; include("includes/invoice-week-module.php"); ?>
</div>
<div u="thumb">Last Week</div>
</div>
<div>
<div style="margin: 10px; overflow: hidden; color: #000;">
<?php $week = 0; include("includes/invoice-week-module.php"); ?>
</div>
<div u="thumb">This Week</div>
</div>
<div>
<div style="margin: 10px; overflow: hidden; color: #000;">
<?php $week = 1; include("includes/invoice-week-module.php"); ?>
</div>
<div u="thumb">Next Week</div>
</div>
</div>
This is my thumbnavigator div block:
<div u="thumbnavigator" class="jssort12" style="left:0px; top: 0px;">
<!-- Thumbnail Item Skin Begin -->
<div u="slides" style="cursor: default; top: 0px; left: 0px; border-left: 1px solid gray;">
<div u="prototype" class="p">
<div class=w><div u="thumbnailtemplate" class="c"></div></div>
</div>
</div>
<!-- Thumbnail Item Skin End -->
</div>
<!--#endregion ThumbnailNavigator Skin End -->
When this error happens, any other JavaScript afterwards doesn't work.