TAZ 6 driver board problem

Hello, I purchased this TAZ 6 in 2017 but my friend does all the maintenance and printing with it. We have had a couple failures of the Rambo control board over the years but now seems a more significant problem. Here is the description he sent me if anyone could provide some advice on what steps to try next:

03/2017 - Original Rambo v1.13L control board
01/2019 - 1st replacement with the same, Rambo v1.13L
03/2021 - 2nd replacement, with updated Rambo v1.14L
So, around 2 years between failures, until the final one, which lasted 20 minutes.
Here are the clues:
Label each connector, take photos, draw map.
Remove old board, install new, connect, double check against photos/map.
Turn on Taz 6 power, display comes up, all looks well.
Fire up Cura, go to Preferences—>Printers—> Upgrade Firmware, success.
Go get a roll of filament, just beginning to start threading it, screen goes dark on Taz 6.
I didn’t even get a chance to load a test print into Cura.
But, at that point, about 20 minutes since Taz power up, there was no power being supplied to:
axis stepper motors
filament drive stepper motor
bed heater
nozzle heater
So, what could go wrong?
power supply
limit switches