Actually, I think it is working.. and I don't think that module is necessary
When you add Open Graph to your site, it can take Facebook a few days to 'see' the new tags. You can run your page through their
URL Debug Tool
to check what they see and update their cache at the same time. Looking at your site, the correct og:image tag is actually in there twice. Once from your module and the other, I'm assuming, because you set it as a default in the Open Graph -> Configuration -> Defaults area.
So, I think you're good to go... but please try again or let us know if you still have issues!
Thanks,
Alex