Having issues with transmitting phone conversations via AUX connection on iPhone 16 Pro.

My wife is a DJ on the radio and sometimes does live interviews while on the air. In the past she would put her iPhone on speaker phone, hook up the Aux cable via an adapter to a 3.5mm jack. Since upgrading to the iPhone 16 a few months ago, she has not been able to do that. The audio will go through from the person on the line but her voice will not transmit. We have rebooted phone, made sure IOS is up to date, and purchased several brands of adapters. The device at the radio station does not have a blue tooth connection or USB connection, only the 3.5mm jack. Any help would be appreciated.