Steering servo doesn't work

Hi all, I am quite new for ardurover project. After a week facing this trouble, I really need your help to keep moving on.

3 weeks ago, everything was working fine but after I updated the new firmware for Pixhawk to 3.0.1, the problem appeared. On Pixhawk I connect 3DR UBlox GPS + Compass Module, PPM encoder and output are steering and throttle to the car. I disabled all ARMING parameter therefore the pixhawk is now having solid blue led. After checking the RC input signal to pixhawk, everything seem to be fine (when I accelerate or steer, the PWM signal changes) but the output signal doesn’t work for steering, only throttle is working. However the throttle also stop after working for a while (I guess because of fail-safe) but steering doesn’t work at all. I stuck at this for more than a week, I hope that somebody could give me some idea to fix it.

Thank you very much.

@Nguyen_Duc_Hoa,
What joysticks are you using to steer and accelerate the rover?
Also, what does your RCMAP_X look like?
Regards,
TCIII AVD

Here is my link to my model and also the joystick
https://www.conrad.de/de/16-elektro-on-road-chassis-bl-rtr-239830.html

@TCIII my RCMAP_PITCH = 2; ROLL = 1; THROTTLE = 3; YAW = 4