Brake light on one side not working (96 Transit van)?

Hi, I have checked the fuse, and replaced the bulb with a new one, and I have put a voltage metre on the side that does not work, and there is no current, yet I tried a continuity test on the brake circuit and it has continuity, which baffles me how can I have a circuit with only power to one side? PLEASE HELP IF YOU HAVE ANY IDEAS, many thanks