Cannot use iOS device as sound input

[yalag]

According to this article https://support.apple.com/en-ca/guide/audio-midi-setup/ams59f301fda/mac

I should be able to use my iOS device connected via usb as a sound input.

But when I follow the instruction the input is shown and I have even enabled it, the bars are even moving but no sound is heard on the mac.

 

[Slartibart]

Did you check under Output the AirPods Max you have connected?

 

[appltech]

In the very article you've provided, it says you need to use the Audio MIDI setup application on your Mac, and yet you're showing us a screenshot of the Sound settings in System Preferences.
Follow the guide carefully. You can find the Audio MIDI setup app in Applications>Utilities (or just use Spotlight).