Assuming you have not configured that specific port as an L-Port, this can happen where the HBA did not completely log on to the fabric. This issue has been known to happen on Emulex HBAs.
To resolve, simply disable and re-enable the port on the SAN switch:
portdisable <port-number> portenable <port-number>
No_Light means there's no link on the port. Usually this indicates a problem with the physical wiring, either a faulty cable, or the TX/RX have been swapped.
No_Sync means there's a link on the port (so technically, wiring is okay), but there's a problem with the actual communication. The most common problem is a mismatch in speed on the switch port and the HBA on the other side. Your best bet would be to set the port's speed (temporarily) to auto-negotiate and see what speed is selected. If this does not work, try manually setting the port fixed to lower speeds.