If an iPad is simply reset from settings - or factory restored with first removing an existing Activation Lock - the lock will remain.
If the iPad is to be prepared for use by a new user, it is necessary to properly prepare the iPad, by removing the Activation Lock, before reseting the device. An Activation Lock can be removed later by the User to whom the Activation Lock relates - but only if they have not removed the device from the AppleID account.
If you are unable to independently secure assistance from the previous owner - whose AppleID currently secures the device by way of the Activation Lock - the iPad is and will forever remain useless to you.
The previous owner requires this information:
What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
Otherwise, here are the Apple support pages that outline the Activation Lock - and the available mechanisms by which it can be satisfied:
Activation Lock for iPhone, iPad, and iPod touch - Apple Support
Turn off Activation Lock – Apple Support
As you will discover, unless you are the owner of the AppleID that was last used to activate the device, you’ll not be able to defeat or bypass the Activation Lock. With documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple may be prepared to assist - otherwise they and nobody here will be able to help you.
If you have the necessary documentation, Apple have introduced a portal though which you may be able to request release of an Activation Lock:
How to remove Activation Lock - Apple Support & start an Activation Lock support request.
However, recovery of the AppleID credentials should be possible…
If you have forgotten your AppleID or associated password, these can be recovered here:
https://iforgot.apple.com/
To recover your credentials, you’ll need access to any one of the following:
- Your primary email address mailbox that corresponds with your AppleID
- Any of the secondary/recovery email addresses that should be configured for your AppleID account
- Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID
Unless you AppleID account has not been fully/correctly configured, or has been seriously neglected, recovery of the AppleID and password should not be difficult.
More information about recovery of your AppleID:
If you forgot your Apple ID - Apple Support
More information about recovery of your AppleID password:
If you forgot your Apple ID password - Apple Support
When you recover access to your credentials, you would be well advised to log-in to your AppleID account from a web browser - and verify/update any email addresses and trusted telephone numbers:
https://appleid.apple.com/
