Guided mode with indoor optical flow only

Hello

hardware: px4flow & lightware sf/10a , indoor
I try to use set_position_target_local_ned to set velocity to control copter from companion computer. I have successfully took copter off in loiter mode and it did well. I can arm copter in guided mode. But copter did not response to set_position_target_local_ned (velocity). Motors just spin in lowest speed. Is there any thing I missed? Really thanks a lot for any hint :slight_smile: