Th1h is on the LIO board. If that and the flat cable were already replaced it can only be a few things. J9500 pin 3 and 5 carry the data so connector can be bad. R5370/71 can be bad or there is still crap under the SMC.
Measure on diode mode on pin 3 and 5 of J9500 to see if traces are not open.
Measure on diode mode on pin 3 and 5 of J9500 to see if traces are not open.