Twitter cards: Not displaying featured image, USM sharing picture, or desc text

I thought it might be the custom (bit.ly) URL shortener causing a problem, but I’ve deactivated that for Twitter and FB shares, and still: if someone clicks Twitter or Facebook icons to share, it’s only sharing the title and the URL, not the featured image (if there is one), not the excerpt (automatic or manual), nor the USM sharing picture or description, if I try using that instead. I checked the page’s source code, and there’s a number of OpenGraph (and Twitter) meta tags it might have chosen, including correct ones obviously added by the USM plugin. So…am I doing something wrong, is there a setting I need to fix, or is this a glitch in the plugin?

The page I need help with: [log in to see the link]