Hello. I don't know if this issue is related to JetPack or to Facebook itself.
When sharing a post, all works as expected. When sharing a page, most of the time "Facebook box" shows only the url - no description and no thumbnail (even if page has images).
I would like to have a "share" button in my homepage that would send to the time line my image and website's slogan as the description. Not sure if this is possible.
I tried to fix this by adding
<meta content="http://www.myurl.com/wp-content/uploads/2013/xx/myimage.jpg" property="og:image"> to my header.php in my theme, but it did not work. I also tried adding an extra function (as instructed here - http://www.wpbeginner.com/wp-themes/how-to-avoid-no-thumbnail-issue-while-sharing-post-on-facebook/) but no luck.
I found many complains from WP users in the Internet, but no working solution. Let me know if this is a lost cause. Thanks.