Looking at the Rotor Riot page for the Vision40 2S the drone should be set up to connect to DJI out of the box.
So assuming that try this.
-In the ports tab in Betaflight
Make sure Serial Rx is enabled on UART 5
-Power On Devices:
Ensure both the DJI Goggles 3 and DJI FPV Remote Controller 3 are powered on.
-Enter Binding Mode:
For the Goggles: Hold the power button until it beeps.
For the Remote Controller: Hold the power button until it beeps.
If you haven't done this already bind the O4 Air Unit to the goggles
Enter bind mode in the goggles.
On the O4 Air unit
Press and hold the bind button until the LED indicator changes to a rapid green flash.
The Goggles should beep indicating the binding was successful.
While connected to Betaflight in Receiver tab verify controller is working.