HexaCopter wrong in arming

I am a student at UClan Cyprus and currently working on a drone project but I am facing some problems. I have got an ArduPilot 2.5 and the frame type and parameters that I am using are APM: Copter V3.3.3 Hexa.
All calibrations are successful, including the radio, motors, compass and accelerometer. I have no other extra features on. I am just trying to make it take off for now. The problem is that, when I am trying to ARM the drone (put the drone in stabilized mode and ready for flying) and then trying to give it full throttle, the motors are spinning for a while and then they stop. This process happens only once, and to do it again, I should unplug and re-plug the battery. Another issue is that, sometimes, when the battery is plugged in, it does not give power to the APM, and the LEDs on ArduPilot 2.5 are off. The parts that I am using are GPS module (3DRobotics), 6 motors each of them is 800KW a power module to give power to the APM, PDB connector to connect motors together, Futaba 6J - 6 channel receiver and transmitter, and ESC for controlling the motor speed.

I would appreciate your feedback on this problem and any possible solution to it.
Thank you for your time.