Charge the headset for at least 30 minutes, then attempt to power it on by holding the power button for 10 seconds.
Try a different charging cable and adapter if the current one doesn't seem to be working.
Perform a hard reset: Hold the power button and the volume down button together for 10-15 seconds until the boot menu appears. Use the volume buttons to navigate to Power Off and press the power button to confirm.
If this fails, try a factory reset as mentioned above.
