On the screen, tap the "i" icon next to your network. Tap Configure DNS and select Manual .
If you purchased the iPad second-hand, the previous owner can remotely remove the lock without needing the device in hand: Ask them to sign in at iCloud.com/find Select the from the list of devices.
This is complex. One wrong command can soft-brick the iPad, requiring a full iTunes restore (which pushes you back to square one). Furthermore, modern Apple servers may eventually re-lock the device if it phones home with mismatched certificates.
The oldest trick in the book for iOS 9 devices is the . This does not remove the lock permanently, but it allows you to access basic functions like the web browser, calculator, and YouTube.
Before diving into "hacks," try the legitimate method.