Setup - ESS, MB3, Mach3 R3.043.062

I have configured Mach3 and when I issue an M3 with a speed the LED for the analog signal on the MB3 lights up. Slower speed, dimmer light. Higher speed brighter light. Should be OK but there is no voltage to the connected wires. I've replaced wires, changed meters, reversed leads, still no voltage.

Anything I'm missing?