3D audio with Garmin GMA 245

I was wondering if there is a trick to get 3D audio to work with the GMA 245? This is the feature that allows two difference source (Radio) to be heard from each ear.
I have turned it on the audio panel and my headset is a Bose but both radios come on both ears.

Assuming you pushed the Pilot button as outlined in the manual to enable 3D mode. I sometimes forget to put the Bose dip switch back to stereo after flying another plane that was wired mono only. Hope it is that simple for you. Otherwise it will be time to check wiring.