Gen 2 won't shift from Park to Drive or Reverse with C1256?

History of major car repairs .. .have replaced main battery pack. Have replaced instrument cluster electronics with reconditioned electrical board. (was giving weird display codes then blank display) Has been good driving for past year. Then after a bit of rain (car is normally parked outside), I stopped at a light and put the car into park. A whole bunch of warning lights came on, along with the red triangle warning light. I stopped at a 7-11 to recycle the electronics (shut car off then on again). The car turned on again, but, the engine didn't turn on, and the car won't shift out of Park (only to Neutral) to Drive or Reverse. It's dead in the water. I've tried holding the brake pedal hard, (the brake lights come on), but, nothing will get the car to shirt into Drive or Reverse. I had the car towed home. (I have a spare car to use for now). I put a OBDII scanner on it and it's showing a C1256 code (brake accumulator low pressure). Brake fluid level is normal. Voltage is 11.5 or so. I tried jumping the battery (replaced about 1-2 years ago), but, it still won't shift into Drive or Reverse? Brake pump seems to be humming away when I turn on start button, and doesn't seem to stop? It seems strange to me that the Brake accumulator would cause the car not to shift out of Park? Could I have a problem with the reconditioned instrument cluster electronics again? Multiple problems at once? I'm trying to figure out an attack plan.