While checking my document i noticed the Twitter card meta data syntax isn't HTML5 valid according to the W3C recommendation.
To get your HTML5 document validated you can change the syntax within file class-twitter.php :
<meta name="twitter should become <meta property="twitter (use the property attribute).
After updating the syntax i did a test via Twitter preview tool. All worked fine.
Site i am referring to : http://advertbanner.com