fullPage.js only showing first section

I'm trying to use fullPage.js but its only ever showing my first section!
I have my sections set up like this

      <div class="section">
        Section 1
      </div>
      <div class="section">
        Section 2
      </div>
      <div class="section">
        Section 3
      </div>

and I inatlize like this

  <script>
     $(document).ready(function() {
       $('.wrapper').fullpage({
         sectionsColor: ['blue', 'red', 'green'],
        });
     });
   </script> 

Can anyone see why it would only show the first section?

Thanks in advance