If its a 4 port FC module, you can't just plug it in. You have to use the USM, and plug it in when it tells you to. I assume that you're direct connecting into the Fabric Interconnects, i.e. not going via fabric switches. This is only supported by Cisco UCS firmware 2.1 and higher. Another thought, can you see light into your fiber cable from both ends and are the fibers round the right way?