- Depending on the smartphone app (which requires HFP (Hands-free Profile)/HSP (Headset Profile)), you will hear a voice from the left unit only, but you may not able to hear a voice from the right unit.
- Check that the connected device and both the right and left units of the headset are turned on.
- An A2DP BLUETOOTH connection is not made between the headset and the BLUETOOTH device. Use the BLUETOOTH device and make an A2DP BLUETOOTH connection.
- If the volume is too low, turn up the volume.
- Check that the connected device is playing back.
- Pair the headset and the BLUETOOTH device again.