flysky fs-a8s sbus

I’m using FlySky Fs-a8s. My goal is to get the RSSI signal. I use the Flysky i6X as a transmitter. I have updated the i6x software for the RSSI signal. My transmitter was 12 channels. I connected my fs-a8s receiver to pixhawk’s RC input. I can see the radio signals in the Mission Planer interface, but the rssi signal doesn’t appear on the MPlanner screen or the i6x transmitter display. What could be the point I jumped?