Tablesaw headers not shown on mobile
Without seeing your html table's structure it is impossible to say why the headers are not showing up. But this is the code from the demo site, so just match what they have done here and it should work.
Make sure you're including their library's CSS. It looks like you might not be, and that could be the problem.
They are using a later version of jQuery (v3.1.1) than the one I selected (v2.1.1), but it doesn't appear to matter.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://filamentgroup.github.io/tablesaw/dist/tablesaw.js"></script>
<script src="https://filamentgroup.github.io/tablesaw/dist/tablesaw-init.js"></script>
<link rel="stylesheet" href="http://filamentgroup.github.io/tablesaw/dist/tablesaw.css">
<table class="tablesaw tablesaw-stack" data-tablesaw-mode="stack" id="tablesaw-5335">
<thead>
<tr>
<th scope="col" data-tablesaw-priority="persist">Movie Title</th>
<th scope="col" data-tablesaw-sortable-default-col="" data-tablesaw-priority="3">Rank</th>
<th scope="col" data-tablesaw-priority="2">Year</th>
<th scope="col" data-tablesaw-priority="1"><abbr title="Rotten Tomato Rating">Rating</abbr></th>
<th scope="col" data-tablesaw-priority="4">Gross</th>
</tr>
</thead>
<tbody>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Avatar_(2009_film)">Avatar</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">1</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2009</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">83%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$2.7B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Titanic_(1997_film)">Titanic</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">2</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">1997</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">88%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$2.1B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/The_Avengers_(2012_film)">The Avengers</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">3</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2012</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">92%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.5B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Harry_Potter_and_the_Deathly_Hallows_%E2%80%93_Part_2">Harry Potter and the Deathly Hallows—Part 2</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">4</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2011</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">96%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.3B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Frozen_(2013_film)">Frozen</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">5</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2013</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">89%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.2B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Iron_Man_3">Iron Man 3</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">6</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2013</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">78%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.2B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Transformers:_Dark_of_the_Moon">Transformers: Dark of the Moon</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">7</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2011</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">36%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.1B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/The_Lord_of_the_Rings:_The_Return_of_the_King">The Lord of the Rings: The Return of the King</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">8</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2003</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">95%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.1B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Skyfall">Skyfall</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">9</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2012</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">92%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.1B</span></td>
</tr>
<tr>
<td class="title"><b class=" tablesaw-cell-label">Movie Title</b><span class="tablesaw-cell-content"><a href="http://en.wikipedia.org/wiki/Transformers:_Age_of_Extinction">Transformers: Age of Extinction</a></span></td>
<td><b class=" tablesaw-cell-label">Rank</b><span class="tablesaw-cell-content">10</span></td>
<td><b class=" tablesaw-cell-label">Year</b><span class="tablesaw-cell-content">2014</span></td>
<td><b class=" tablesaw-cell-label"><abbr title="Rotten Tomato Rating">Rating</abbr></b><span class="tablesaw-cell-content">18%</span></td>
<td><b class=" tablesaw-cell-label">Gross</b><span class="tablesaw-cell-content">$1.0B</span></td>
</tr>
</tbody>
</table>