Having trouble with an iPad you just bought second-hand? A common problem with used Apple devices is that buyers can’t get them to work properly, due to Apple’s Activation Lock.
Apple created the Activation Lock feature to protect against device theft. When an iPad, iPhone or newer Apple computer is properly signed into iCloud services, Activation Lock is also silently enabled. From that point onward, the device is bound to the owner’s AppleID.
This means that, even if the device is erased/restored/reformatted, it is still tied to that AppleID. Activation Lock will stop any other AppleID from signing in. The iDevice will be unusable, until the original owner’s AppleID is logged in. And Apple Support will not help you solve this, unless you can show original proof of purchase.
If you’ve bought a used Apple device and encountered this block, it may mean the device was stolen! Or it could just be an honest mistake: Ask the seller to go to their iCloud page and Remove the Device from the Find My page. If they can do that, the device will then accept a new owner’s AppleID just fine. If they won’t… I hope you can reverse the sale and get your money back.