HTML Snippets not working in Sublime Text 3

This is because on line 4 in the class attribute of the <div> you open with a curly brace { but close with parentheses ).

To resolve the issue use this snippet (removed the parentheses and added a curly brace)

The snippet

<snippet>
  <content><![CDATA[
    <li class="timeline-inverted"><!--   ▾ Here -->
      <div class="timeline-badge ${1:type)"><i class="fa fa-calendar"></i></div>
      <div class="timeline-panel wow fadeInDown">
        <div class="timeline-heading">
          <h4 class="timeline-title">${2:year}</h4>
        </div>
        <div class="timeline-body">
          <p>${3:data}</p>
        </div>
      </div>
    </li>
    ]]></content>
    <!-- Optional: Set a tabTrigger to define how to trigger the snippet -->
    <tabTrigger>tmeln</tabTrigger>
    <description>timeline-body</description>
</snippet>

Hope this helps!