Nikon D700 Flash sync terminal working properly?

I was in a studio photography class today and after setting up the 3 lights, plugged the flash cable directly into the dedicated flash sync terminal but the flashes didn't fire. When I used the hot shoe adapter (which enabled me to plug the sync cable into there instead) the flashes went off fine.

Is there a Nikon setting that I should have adjusted or is the sync terminal broken?

I have never used a PC connection on a dSLR, Nikon or other. You will probably get an answer from Nikon. 800. NIKON-UX

When shooting in the studio, I use Pocket Wizards to trigger my flashes.