I can start calibration and see the waterfall lights briefly, but then they turn off.

Check your positioning (seated with leg at 90° angle) and device (upper calf, 1-2” below the knee). Electrode should be making complete contact with the skin. Try smoothing the electrode over your skin (while it is snapped to the device), before securing the sports band.

If you are still having an issue calibrating your device, please contact our Customer Care team at 1-800-204-6577 Monday thru Friday 8am to 8pm and Saturday 10am to 2pm Eastern standard time.