Thanks for that!
Yes we did the ESC calibration, but the problem remains.
Can you confirm, that our motors should start spinning, after arming the copter in manual mode and raise the throttle? We want to be sure, that we did not miss any step, that has to be done before the motors can be started.
@farhang do you have any other idea, what the problem might be?
Our Problem sounds similiar to the situation discussed in this topic: Pixhawk 2.1 Cube Black / PX4 V1.11.1 No PWM Output when Armed
But we did not change anything within the firmware.