Detected 0 radio channels. To Operate px4,you need at least 5 channels

PX4 Autopilot Configuration & Flight Modes ⚙️
1

I am using FLYSKY radio controller FS-IA6B. Getting the following error
Detected 0 radio channels. To Operate px4,you need at least 5 channels.

2

That usually means that the FC is not seeing the radio channel inputs from the RX.
How have you connected the RC to the flight controller?