Judging by this, Pin 1 relevant circuit has been open-circuited. Pin 1 of J6400 is connected to Pin 2 of the speaker amplifier IC U4900 by way of Pin S162 on cylinders around the edge of the lower layer.

So our next move is to check the circuit carefully. Disconnect flex cables on the motherboard and take out the motherboard. Fix the motherboard to the Holder. Heat with Hot Air Gun at 360℃, air flow 65.