SOLVED: og:image not in source code.

Murcel,
It looks like you're using K2. JFBConnect currently only automatically inserts the image tag if the image is inside the article text, not if you're using K2's Image tab to set the primary image for the article. In JFBConnect v4.1, coming out this month, we'll be adding the ability to pull the main image from K2 as well.

As for the JFBCGraph tags, my best guess for why they're not working is that you're using the System - Cache plugin. If so, please make sure it's ordered after (higher number) than the JFBCSystem plugin. If that's not the issue, then make sure you're adding the tag like follows:
{JFBCGraph image=http://bospace.de/link-to-image.jpg}
If you have a key set in the Social->Misc section, you should use that as well:
{JFBCGraph image=http://bospace.de/link-to-image.jpg key=12345}

Hope that helps, but if you're still seeing the issue, just let us know!
Alex

Marc,
K2 is supported very well in JFBConnect, just the "Primary Image" for an article/item isn't currently supported. We will automatically create the title and description as well as image tag (if the image is in the article contents). In 4.1, we'll support the Primary Image as well and use that. Until then, we won't automatically add the image tag, you'll need to do it manually.

Glad you figured out the tags. The key is there to prevent user's from adding arbitrary tags, if there is user generated content on your site. While it's unlikely, we always want to protect JFBConnect user's however we can!

Finally, please consider leaving a rating and review for JFBConnect, or our support, on the Joomla Extension Directory:
extensions.joomla.org/extensions/social-...ook-integration/7215

Thanks, and good luck,
Alex