Make sure that the battery is charging and operating properly. If the battery is not the problem then you may want to check the razor head for hair buildup. The razor will not shave as well if it has too much hair inside the head. If it is clean and the battery is charged, then it may be time to replace your motor
First, you want to make sure the battery is actually being charged. Make sure it is plugged into a working outlet and make sure the charger itself is not damaged. If everything seems like it is charging they way it should be and the razor still does not function, you may need to replace the battery because it is nearing the end of its life.