Some customers who use the RingCentral Mobile app version 8.4.2 experience hearing no audio during a VoIP call. It can happen on any of the circumstances:
User switches the audio source from Speaker to iPhone
After switching the audio source from Speaker to the iPhone's built-in handset, the User can still hear the noise coming from the other side, but the party on the other end cannot hear any audio.
Audio suddenly stops during a call
Suddenly, there is no audio during a call on both the User and the other party's end.
Losing the audio while on a Mobile app call on an iOS device rarely happens. You can try the following solutions, should you experience losing your audio as described in any of the two scenarios mentioned above:
Kill the RingCentral Mobile app, then re-launch the app.
If Solution 1 does not work, restart your iOS device.
Overview of VoIP Calling on the RingCentral Mobile app
Call Interruption on iOS
RingCentral Integrated Calling