QGroundControl detected 0 radio channels

Good day, when I was following the setups, I cannot calibrate my RC, where QGroundControl gives errors: “Detected 0 radio channels, To operate PX4, you need at least 5 channels”.

Here I have COEX A8S v.2 receiver (with a wire connection without PPM-port) connected to PIXRACER R15 AUTOPILOT on port RCIN.

The LED red light on receiver(A8S) stopped blinking once I turned on the transmitter, but there are no information shows on my RC screen.

I tried to fully connect all 4 ports to RCIN, but still not working.

SBUS to RCIN doesn’t quite seem right. Shouldn’t it be PPM to RC In?