Make sure the headset volume control is turned up. Rotate the volume wheel on your headset to increase the volume. If you're connected to the PC via USB, check that the default device is selected under Control Panel > Sound > Playback. Select JBL Quantum 400 Game, right-click, and select "Set as Default Device".  Check on the top bar of the JBL QuantumENGINE whether your headset's game-chat balance dial is set correctly. Check the JBL Quantum 400 Game device and make sure it is not muted or turned all the way down.