JFBC Comments suddenly not showing on site

I just tested that page, and it's working fine for me in Chrome and Firefox. Can you check that you don't have an add-on/plugin installed that's meant to disable social networks. Extensions like Ghostery (and many others) will intentionally disable Facebook integration features.

I'm not sure what else it could be. Looking at your page, everything seems correct. The best suggestion I'd have is to try from a different computer to check whether it's specific to the one computer you're testing from or not.

Keep me posted, and good luck,
Alex