Right. So you've configured that button to post the link
https://shar.es/1Fmi4l which is not the same as the link
http://www.backtothefuture.com/news-events/latest-news/Tom-Wilson-%E2%80%98Biff%E2%80%99-From-Back-to-the-Future-To-Make#sthash.RU1gHgz5.FKJ0TXV1.dpbs which is the one that I shared.
Validating the first link results in the following errors:
ERROR: Fetching the page failed because it resulted in too many redirects.
WARN: this card is redirected to http://www.backtothefuture.com/news-events/latest-news/error
So, that link is broken and no card can be shown. The actual page and card work fine.