There's nothing in the cord except wire so the problem must be the cord / camera interface. Based on the description I'd check how the cord is seating in to the hot shoe, contacts, etc.
Was it working OK previously? Have you tried M mode on the flash?
1) check the cord with a multi-meter
2) TIghten the screws holding the hot shoe plate on the camera body
3) TIghten the screws holding the hot shoe plate on the off camera cord