D'oh! I found that the instructions had simply confused me. There are two very similar header-pin layouts. Both have eight pins (the right number for all the sensors), and both have similar patterns of other pins (three on one end) next to them. I needed to wire up to the ones that sat parallel to the power input connectors, rather than the ones in an uncluttered area along one side of the white board.Once I got that right, the sensors did get read up properly by the robot.I am feeling much better about this purchase, now.