I think I've pinpointed the cause of the problem. When we try to build up the URL to send for the autopost, we were getting redirected by the language switcher which is active on your site. The URL was then not built up properly because I wasn't expecting this redirect. I've added some code to respect the language and it seems to be creating the full path now. I've tested by adding debug statements but didn't actually post to your FB page as I didn't want to spam it with testing. The only file changed on your system was the /libraries/sourcecoast/openGraphPlugin.php file in the method that was mentioned above.
[Edited to add] Actually I just realized the auto-post was going through to your LinkedIn Company page. You will have to delete those messages from your company page. I've already deleted the K2 item that I created as a test, but the link in LinkedIn went to the correct K2 item.
Could you go ahead and try to create a new item or re-publish one that hasn't been auto-posted yet? I've removed the debug statements so it should post now. Let me know how it goes.