Transmitter yaw not cause any movement of singlecopter's flaps

[teachthegrace28 (kim)]

Hi
I’ve tested pitch, roll successful.
https://ardupilot.org/copter/docs/singlecopter-and-coaxcopter.html

But, flaps didnt follow yaw control and didnt move.
What does make this problem and how can I fix it?
Thank you for help