You haven't charged it long enough. Plug the charger in and wait 24 hours. It's a charger, not an external power supply. If you charge it for an hour, then turn it on, it's charged just about enough to turn on - that drains the little bit of charge in the battery and it turns off. Laptops can run on their "chargers" (which are actually external power supplies) without even having a battery in the laptop - phones and tablets can't. Most phones and all tablets need more power to run than a charger port can supply.