Motors Non-Responsive

Hi Forumers

Im new to this site and was wondering if someone could help me, I have built my own drone and am using a Pixhawk PX4 Pro, it has all been set up inaccordance with the frame type, (Quadcopter +), Radio, Sensors etc and I am using QGroundControl software.

When arming the drone, all of the motors spins at a high RPM, however, when using the Throttle Stick, the motors do not change in speed.

Is there anyone out there that can tell me what I have done wrong or whether you are able to help me rectify this problem, many thanks in advance