How Did Levin's Experiment Work?

Two out of three ovens had failed, and that was before levin's experiment had even run. In the second oven, the same thing happened again. And what about viking, too? They had another lander elsewhere on the planet. What did its result show? Michael brooks explains the g c m s experiment run four times in total. But no trace of organic material was detected in any of the four runs. And no organic material, in the team leader's interpretation, meant no life. So with two tests saying life had been discovered, and two apparently saying that it hadn't, mission leaders announced to the public that they had foundt no evidence of life on mars