I'm having similar problems, although I'm trying to get it to display any activity not just a specific page's activity. Anyways, one thing that I have discovered is that for the 'data-site' tag you need to use a domain (ex. www.facebook.com), using 'www.facebook.com/groups/2379953649/' doesn't seem to work because it is giving more info than just the domain, subdomains (ex. graph.facebook.com) will also work, but the domain needs to have facebook activity, ie. a link has been shared from that site on facebook, etc.
Sorry for the wordy answer, hope it helps, and if anyone notices that anything I have stated is incorrect please correct me.