Using Simulink-based Quadcopter controller; detected 0 radio channels

Hello everyone!
I’m currently working on my FYP for which I’ve built a quadrotor controllers in Simulink.
It works in Simulink and in F450, but when I upoad it onto the Pixhawk and connect to QGroundControl, it doesn’t let me calibrate the RC.

The error I get is “Detected 0 radio channels. To operate PX4, you need at least 5 channels.”
I’ve also tried the example controller model provided by MATLAB, but I’m facing the same issue there.
I’m using the RC block provided by the Simulink PSP toolbox.
When I use the ArduPilot firmware, the RC connects and calibrates just fine.

I’d big time appreciate some urgent help, as my FYP is due very soon.

The RC I’m using is the FLYSKY FS-i6X with the FS-iA6B receiver, and Pixhawk 1.