Connecting aux servo to pixhawk 4

I used quadcopter (generic quadrotor) f450 with pixhawk 4 , and i used pwm auxiliary pins from (aux1 to aux 4 ) , and i changed qground parameter to use actuators instead of motors, then i want to use servo , so i connected it to pin (pwm out aux 5 ) with external 5v battery, everything works good and i can control the servo from qground, but when i tried to control servo from Rc ( channel 5 ) I can’t as there is no response….
Anyone can help please ?