My laptop lenovo u330p

Hello, my lenovo has got an inbuilt battery and I always left it in sleep mode after use .so one evening I was gonna use it and it shutdown all of a sudden .tried to press the power button to show some power on the led but instead it failed yet it has battery cause I notice that when I plugin the charger. Its been days trying to find a solution cause I've tries the detaching of the battery and pressing g the power button.its failed.