I have been everywhere, on internet but can't find the solution! Since a few months ago, when I share my blog on facebook, it does not show a thumbnail image anymore. Before that, it worked fine. I know I am not the only one in this case. Do you know how I can do to fix the problem? Your help would be very much appreciated!
Try adding a thumbnail pic externally via the "Attach" option below the space where you write messages, It should work probably ....
You can try RSS Graffiti in facebook app. It auto publish your blog entry acc to your RSS feed to either your fb profile or fan page with thumbnail and short description of your blog entry