Hello,
In order to use bidirectional audio on the MixingLink, you’ll need to use a TRRS 1/8 cable, and the USB C adapter will also need to accept TRRS connections. Can you please confirm you are using both of those?
You also may need to open the camera app first, and then connect the USB adapter for it to recognize the USB input: https://apple.stackexchange.com/questions/229346/how-do-i-record-video-on-ios-with-external-audio-interface
