Payload place function doesn't work

ArduCopter Copter 4.0
1

HI

Today I tried several times place payload but It doesn’t work.

What did I try.

  1. I matched servo 13 = parameter 28(Gripper) same time RC7 = 17 (Gripper)
    -> No work.

  2. only Servo 13 = Parameter 28 (Gripper) -> No work.

  3. only RC 7 = Parameter 17 (Gripper) -> No work.

캡처
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How should I do? I hope any body give me a tips.

Thank you in advance.