Check the battery polarity. Match the "+" and "-" polarity symbols on the battery to the markings inside the battery compartment
Power troubleshooting
Verify that the battery compartment is free of debris. Use compressed air to blow any dust or debris out of the battery compartment. Use rubbing alcohol and cotton swabs to clean the contacts within the battery compartment
Try installing a new battery
You may need to replace the battery. The LED light will blink when the battery has approximately five hours of charge remaining. When this occurs, replace the battery
Yes, this is normal. You may hear a slight pop when you turn the headphones on. This occurs as the noise reduction circuitry powers up