Finally got this to work. Aux switch for the GE /Jasco 3 way zwave switch seems to be everyone's problem. It should be:
Black Hot and black load are nutted together and NOT connected to Aux switch.
Then it's
Green to copper
Yellow to traveler
And dun da da da - neutral to white
That's right, you need to have a neutral in your box.
With the blacks nutted together in the box, you can install the Aux switch in box A or B.