Facebook Like Box not working

Facebook gives you default code to insert into a website that will display a Facebook Like box (including recent posts) to your fan page.

The code includes a javascript call

<div id="fb-root"></div>
<script>(function(d, s, id) {
  var js, fjs = d.getElementsByTagName(s)[0];
  if (d.getElementById(id)) return;
  js = d.createElement(s); js.id = id;
  js.src = "//connect.facebook.net/en_GB/sdk.js#xfbml=1&version=v2.0";
  fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>

and some hmtl to display the result

<div class="fb-like-box" data-href="https://www.facebook.com/myfanpage" data-width="400" data-height="600" data-colorscheme="light" data-show-faces="false" data-header="false" data-stream="true" data-show-border="true"></div>

Previously I found that inserting both of these pieces of code together in a page was sufficient to display the box as expected.
On one site using ‘Able’ theme this works perfectly on WP4.0 but on another site that is running ‘Twenty Fourteen’ this does not work.

Can anyone help me understand what has changed / what I’m doing wrong?

Thanks