I think i figured it out. J1 on the PMDX-126 controls J4 on the PMDX-134.
Since I was testing one stepper hooked up at a time, it was originally wired as (I expected) J1=J1. The way the enclosure was laying on the bench, I didn't notice the activity light flashing on the drivers until I started trying the other axis. /light bulb moment....
Now, if this is a jumper or ribbon cable issue please let me know.