Make sure that the content of the file is well-formed.
The content of the XML file
should look like
this:
<div id="google-plus">
<!-- Place this tag in your head or just before your close body tag. -->
<script src="https://apis.google.com/js/platform.js" async defer></script>
<!-- Place this tag where you want the +1 button to render. -->
<div class="g-plusone" data-annotation="inline" data-width="300"></div>
</div>