OSHPark did a great job as always, unfortunately, I had a brain fart and forgot that the AVR microcontroller under the shield connects to the RS-422 transceiver through the 74LVC07 buffers I used. I was trying to use the buffers IOFF state to allow the Pi Zero to be powered off without pulling down the RS-422 bus.

When U3 (74LVC07) does not have power the serial RX and TX from shield can not reach the RS-422 transceivers.

For testing, I need to cut U3 power from the PI3V3 node and bridge it to the +3V3 node.

So far this hack is working, but I have another board on the way so this will soon be back on a spin loop thread.