LG WM3997HWA Combo Washer/Dryer LE error, not spinning, then no power, then no display

[apzpz]

Hi! I am trying to fix an LG WM3997HWA All-in-One Washer/Dryer Combo.

Summary: LE error, then died entirely, replaced main PCB, now powers on but display not working

1. The washer suddenly presented an LE error (locked motor error) mid-cycle.
2. I power off/on and ran the diagnostic test. It failed to spin and again presented an LE error.
3. I ran the diagnostic test again and suddenly the entire unit powered off. It was completely dead at this point. I tried holding the power and start buttons for a few seconds while unplugged to "reset" but this had no effect. It's completely dead at this point.
4. I replaced the main PCB with the part number specified in the service manual (EBR75640321).
5. Now it will power on and off with the power button, but the display is not working and none of the other buttons have any effect.

- The old main PCB looks like a component failed (see attached picture).
- All wires from main PCB to display PCB pass a continuity check.
- I don't think this model has a hall effect sensor.

Any ideas? Is the replacement main PCB faulty? Has the display PCB failed also? Thanks!