- Check that both the headset and the connected device (i.e., smartphone) 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.
- Turn up the volume of the headset and the connected device (i.e., smartphone).
- Check that the connected device is playing back.
- If you are connecting a computer to the headset, make sure the audio output setting of the computer is set for a BLUETOOTH device.
- Pair the headset and the BLUETOOTH device again.
- Check that the headphone cable is connected firmly.