Twitter Card Tags Missing on Home Page?

I’m probably missing something really obvious but the Twitter Card tags are not displaying on my home page. They appear beautifully on other pages but just not the home page.

I’m guessing this is either a clash/incompatibility with the Jetpack plugin or more likely, something in the theme.

On my home page I am seeing:

<!-- This site is optimized with the Yoast WordPress SEO plugin v1.4.15 - http://yoast.com/wordpress/seo/ -->
<title>United World Schools Charity - A different school of thought</title>
<link rel="canonical" href="http://www.unitedworldschools.org/" />
<link rel="next" href="http://www.unitedworldschools.org/page/2/" />
<link rel="publisher" href="https://plus.google.com/103701684245564891999?prsrc=5"/>
<meta property="og:locale" content="en_US"/>
<meta property="og:type" content="website"/>
<meta property="og:title" content="United World Schools Charity - A different school of thought"/>
<meta property="og:url" content="http://www.unitedworldschools.org/"/>
<meta property="og:site_name" content="United World Schools Charity"/>
<!-- / Yoast WordPress SEO plugin. -->

But on other pages I am seeing:

<!-- This site is optimized with the Yoast WordPress SEO plugin v1.4.15 - http://yoast.com/wordpress/seo/ -->
<title>Volunteer - United World Schools Charity</title>
<meta name="description" content="Learn how you can volunteer with United World Schools Charity in Cambodia, and around the world."/>
<link rel="canonical" href="http://www.unitedworldschools.org/get-involved/volunteer/" />
<link rel="publisher" href="https://plus.google.com/103701684245564891999?prsrc=5"/>
<meta property="og:locale" content="en_US"/>
<meta property="og:type" content="article"/>
<meta property="og:title" content="Volunteer - United World Schools Charity"/>
<meta property="og:description" content="Learn how you can volunteer with United World Schools Charity in Cambodia, and around the world."/>
<meta property="og:url" content="http://www.unitedworldschools.org/get-involved/volunteer/"/>
<meta property="og:site_name" content="United World Schools Charity"/>
<meta property="og:image" content="http://unitedworldschools.org.gridhosted.co.uk/wp-content/uploads/2012/10/Vera-Volunteering-300x269.jpg"/>
<meta property="og:image" content="http://unitedworldschools.org.gridhosted.co.uk/wp-content/uploads/2012/10/Bella-UWS-Volunteer-and-Leak-UWS-Cambodia-Community-Teacher-Trainer-300x241.jpg"/>
<meta name="twitter:card" content="summary"/>
<meta name="twitter:site" content="@TeamUWS"/>
<meta name="twitter:domain" content="United World Schools Charity"/>
<meta name="twitter:creator" content="@TeamUWS"/>
<!-- / Yoast WordPress SEO plugin. -->

Is there something I need to add to the Home Page template to get the Twitter tags working?

Many Thanks
Hugh

http://wordpress.org/plugins/wordpress-seo/