I would take a look at the schematic and check if you're getting all the correct voltages using a multimeter.
If you find that one of the components isn't outputting the expected value, it may have been shorted. I don't know if you have the tools or expertise to replace individual components though - IF you can even find the component for sale anywhere.
I ran into this same issue, the only thing that the PBP was doing is giving me a blinking red charging light. I did a re-seat of the EMMC and a few reconnects of the battery and it came back alive; so I'm not sure what was going on.
EDIT:
I reckon there's a very low chance, but if you happen to be find yourself in Tokyo, I can take a look at it for you!
If you find that one of the components isn't outputting the expected value, it may have been shorted. I don't know if you have the tools or expertise to replace individual components though - IF you can even find the component for sale anywhere.
I ran into this same issue, the only thing that the PBP was doing is giving me a blinking red charging light. I did a re-seat of the EMMC and a few reconnects of the battery and it came back alive; so I'm not sure what was going on.
EDIT:
I reckon there's a very low chance, but if you happen to be find yourself in Tokyo, I can take a look at it for you!