Please check if the VOLUME can be adjusted on the source device.
Kindly perform a reset procedure:
1. Turn off the HD77 and charge it for at least 2 hours.
2. Go to the Bluetooth menu on your source device and delete all saved devices from the list by clicking on "Forget this device".
3. Turn off your source device then and then turn it back on.
4. Turn on the speaker
5. Try to press and hold the VOLUME UP and the VOLUME DOWN buttons on the HD77 simultaneously for 5 seconds.
6. Repeat the steps for pairing.
If the issue still persists and you want our further assistance, please click Contact Us. We will help!