If possible, change cable, charger and power outlet. If your iPad still doesn't charge, take a look at the lightning port. If you see some dust or dirt there, remove it with a clean, never before used toothbrush, and try charging again.
If this doesn't help either, try force starting your iPad. That's performed by pressing and holding Home and Power button simultaneously until the Apple logo appears. As soon as you see it, let go of both buttons. Your iPad should power up on it's own.
Hope that helps.