Interruption

The system took the microphone away.

On iOS: a phone call, Siri, an alarm, another app's audio session that does not mix with yours, or the app being suspended in the background. On Android (API 29+) the system silenced the recorder, most often because the app went to the background without a microphone foreground service, or another app with priority started capturing. Below API 29 Android reports no interruptions.