First thing to check is the cable and charger. There aren't too many things that prevent an iPad from charging.
1. Bad cable. Try a different Apple or name brand cable.
2. Bad Charger. Try a different known good charger plugged into a known good wall outlet.
3. Dirt, lint or fuzz in the connection ports. Check and carefully clean with a wooden toothpick is needed.
4. Software failure. Reset the iPad. Press and hold both the Home button and the Sleep/Wake button continuously until the Apple logo appears. Then release the button and let the device restart. You will not lose data doing this. It's like a computer reboot.
5. Hardware failure. Make an appointment at an Apple Store to have your device examined by a technician. Or contact Apple Support. Be sure to back up your device before taking or sending it to Apple.