Battery Unavailable error in ESCs calibration

I am trying to use QGC to calibrate my ESCs, I follow the steps as prompted and it always reports the error Battery Unavailable.
My F450 drone does not have a power module, the Pixhawk is powered by the ESC.

I would like to know what is causing this problem? How should I be able to calibrate my ESC.

My procedures:
1 Disconnect the battery
2 Pixhawk connected to computer via data cable
3 Click the calibrate button
4 QGC reports “Battery Unavailable” error

Firmware: PX4 Pro Stable Release v1.12.3