KT3 Help needed to unbrick KT3

[buyifan43]

I tried to flash Android on my KT3, but after tapping the extension in KUAL, my device rebooted and stuck at a white screen.
I tried to solder to TTL but found there's NO OUTPUT on hard rebooting/connecing power cable
When i try to use usb boot by shorting testpoints, the serial port returnd this

In:    serial
Out:   serial
Err:   serial

Help please, thank you all so much

[buyifan43]

Use windows compability mode and a new FTR232L serial adapter i successfully loaded the uboot and flashed it through fastboot. Then it goes normally by flashing the other partitons.