Check if the light on charger stays on when its plugged into the system.If yes,disconnect the charger,remove the battery,press and hold down the power button for 30 seconds.Reconnect the battery and charger,turn on the system and see if there is any change. For better and effective solution please watch troubleshooting instructions in [https://guideusermanual.com/product-name-thinkpad-t440-manual&po=331274&lang=English|Lenovo ThinkPad T440 Manual].