iPad Pro 12.9, USB Data Transfer Failure

iPad Pro, USB Data Transfer Failure

This is the iPad Pro 12.9-inch 4th generation model.

The connection to the computer via USB-C port is not working. My computer doesn't detect the ipad at all. (The same goes for ipad recovery mode.)

Currently, iPad is not a matter of computer trust because it has completed a factory reset.

I've also replaced the cable, but it's the same as the A to C cable or the C to C cable.

The symptoms are the same when I try on another computer (both Windows Desktop/laptop and macbook air M1)

Eventually, I disassembled the iPad and replaced the dock flex cable, but the symptoms didn't change. And I checked the logic board with a multimeter, but I couldn't check the short circuit/abnormal heat in components such as capacitors.(I have not yet checked the metal shielded part.)

Surprisingly, all other features are normal. There is no abnormal power off / panic full crash and the battery works well.

1. PD Charge - OK. Charging speed is also normal.

2. External Storage Connection - OK

3. External Monitor Mirrors - OK

4. USB-C Hub Connection - OK

I don't know the cause...Is it a failure of the USB IC?