Some iOS users whose device version is 9.0.4 or later are unable to answer or decline a call using a Bluetooth device or a wired headset when running the RingCentral Mobile app. Some iOS users with iOS 9 or iOS 10 may also experience this when Integrated Calling is disabled on the RingCentral app.
It happens on any of the following circumstances:
Using a Bluetooth device
The incoming call cannot be answered when the button in the Bluetooth headset is pressed.
Using a Wired headset
The incoming call cannot be answered nor declined when the buttons in the wired headset are pressed.
Follow the steps below if you experience being unable to answer or decline a call as described in any of the scenarios mentioned above:
Upgrade your iOS device to the latest version.
Enable Integrated Calling in the RingCentral Mobile app.
RingCentral Integrated Calling
System Requirements for the RingCentral Service