I am working on a VoIP based PTT app. Uses 'voip' apns notification type to get to know about new incoming PTT call. When my app receives a PTT call, the app plays audio. But the call audio is not heard. While checking the phone volume, the API [[AVAudioSession sharedInstance] outputVolume] returns 0. But clearly the phone volume is not zero. On checking the phone volume by pressing side volume button, the volume is above 50%.
This behavior is observed in both app foreground and background scenario.
Why does the API return zero volume level ? Is there any other reason why the app volume is not heard ?