RE: KKmulticopter board issue
Hi,
One possibility is that transmitter throttle channel needs to be reversed. If the KK board thinks your throttle is full, it won't arm.
Also, I couldn't tell from the video but only use the red center wire for BEC on M1 to the KK board. M2 - M4 need to have their BECs disconnected by cutting the middle wire or pulling the pin on the control cables.
Good luck!