If the device does not appear to be charging, the two likely sources are either the charger itself, or the battery. When you plug the charger in to the device, an indicator light should turn on showing that the device is being charged. If this light does not turn on, you should check the charger in another device to see if the charger is working. If the charger is in fact working, the problem is likely the battery. To further confirm, if you are able to hear the fan of the device spinning but the screen wont light up, the problem is the screen, if the device still seems dead, I would replace the battery.
If you need further assistance, please refer to the Troubleshooting Page.