Inquiry on Pixhawk 2 + Taranis Qx7

Hello All,

I have Tarot drone connected with Pixhawk 2, and Cube Black with Taranis Qx7 RC.
When I switch arm, I hear a beep sound and Receiver is green color, but the motor doesn’t start.

Note: I’m not using betaflight.

Please help what could be wrong here?

Thanks !!