This unit can not be powered up. It has polarity reversal prevention, so it should not fried due wrong polarity.
First check, it has AOZ1282 Buck regulator. Its input is zero volt. The input is fed through 100 Ohm resistor. But its also a diode in reversed position as polarity protector. This diode is found to be short and causing the buck converter did not get proper input.
Removing this faulty diode solved the problem.
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