I tried to activate AudiSession in incomingPushResult method and then didActivate was called in background even though AudioSession threw an error.

No, I am not activating or changing anything in AudioSession. I have pretty straightforward setup; recording an audio using AVAudioEngine and sending to the server (which is running locally for now). And when PTT notification arrives saving url to audio file in incomingPushResult, then downloading and playing that sound using AVAudioPlayer when didActivate is executed. It's working fine on foreground, but when app goes to background incomingPushResult is called as expected but didActivate is not for some reason. Am I missing anything in my setup?

I am having the same issue, channelManager(_:didActivate:) is not called in background. audio is included in UIBackgroundModes. So, it seems the issue in PTT framework itself. I am testing on debug mode, but that shouldn't be a reason, right?