J-PAC Question

[Xicor]

I've got a JPAC connected to my motherboard through PS/2, and as a quick test I connected the JAMMA terminal and ground for Player 1/Up (right now I haven't wired all the buttons/joysticks). Moving the stick up doesn't do anything on the computer (in this case, entering the UP ARROW). When I boot my PC, the SELFTEST LED flashes twice quickly and remains lit until I shut down the computer. What worries me, however, is that the SYNC IN LED is never ever lit. The SYNC ON LED works fine and I get a clear and working picture on my monitor. So, any suggestions? Do I need to have all my connections wired in order for the J-PAC to function?