I've been struggling a lot with getting Facebook to properly render the preview for our site. I think it has something to do with the Social settings. I have spent hours on this trying different methods of entering the meta tags myself, or using your plugin. Nothing seems to work. Finally got the preview image to load, but nothing else is rendering in the preview. You can try yourself by testing http://www.rxapps.com
Would love any help you can provide. Thanks Joost.