1) LCD contrast may be affected by temperature. If temperature is too high, there will be no display on the screen; then rotate the knob on the side of the console until data appear.
2) Power supply is not well connected, since there is no built-in battery and instrument is power supplied by external battery.
3) Battery voltage is too low, please recharge the battery.
4) Power line is not well connected. Please check the power supply plug.