Open as in open circuit. Broken pin, corroded pin, broken wire, maybe even a broken trace on the display (though less likely than something in the cord). Somewhere the path that reports the bayonet to the display is interrupted. Of course it could just be a component fault on the board in the display but I personally think that's less likely.
The idea of trying another cord is an excellent one to try to isolate the problem. Is there anybody you know who has the same device and can lend you a cord to try? Or do you have a multimeter and can measure the resistance (ohms, right) from pin to pin on the cord? Resistance should be infinite
Best of luck.