Won't go on my 5d so I tried on my 1dmk2 same problem. The cord looks ok to me.
I never used it. Been sitting there for some time. When I look at it the end which goes on the camera looks good. I will check again tonight. Since I sold my mini/flex I have no way to use my off camera 550ex at > 1/200 with my 5d. I just wanted to take some shots with 35L at f1.4 during the evening so thought I could use this cord.
BTW - The regular 3 feet cords that have work fine.