I've created an example app to demonstrate my problem. It can be found here: https://github.com/egeniq/ptt-audio-activation-test-ios To reproduce, do the following: Change team selection in Xcode. Run the app. Choose join. Tap on the "Set remote participant NOW" button. See in the log output that the audio session gets activated. Tap on the "Clear remote participant" button. See in the log output that the audio session gets deactivated. Tap on the "Set remote participant after 5s" button. Immediately go back to your phone's homescreen. After 5s see in the log output that the remote participant is successfully set. However also note that no audio session activation occurs.

I indeed used a simplified example for demonstration purposes where I didn't add the microphone permission and audio session setup. In my real application I do. However, your answer did trigger me to check that code again, and I noticed that I accidentally added .mixWithOthers to the options. And it seems that causes the audio session not to get activated when running in the background. So I removed that option and now everything is running fine! Also great to hear that it is ok to keep things running in the background when there is an active PTT session. It indeed improves the conversation flow a lot. Thanks!

Wow, thank you for the extensive background information!