With the newest release of JFBConnect, the Open Graph integration has changed a bit. I'm not sure if that's the cause of the problem, but can you try any of the following to see if it fixes the problem:
* In the Open Graph -> Settings area of JFBConnect, add a default image. Something like a logo is a good default image to use for all of your pages. You can enter it into the Defaults box like:
image=http://www.yoursite.com/path-to-logo.jpg
* Upload and enable the Open Graph - Joomla Content plugin included in the latest v4.3 zip package.
Basically, Facebook has recently become very rigid about having an image included in your Open Graph text. The new Open Graph system is much better at including an image in a broad range of extensions, but you need to install and publish the correct plugin(s) for those extensions.. including Joomla articles.
Let us know how that goes, and if you need more information, we'll be here!
Thanks,
Alex