activation lock

I echo Z's curiosity, but regardless ...

For you to not have ongoing problems with your iPad going forward, the device needs to be completely "expunged" of the previous owner, and then setup for you and your own Apple ID.

The old owner needs to do the following:

https://support.apple.com/en-us/HT201351

You'll know when it's REALLY ready for you when you turn it on and it says, "Set up your iPad"

Activation Lock is a theft deterrent. It wouldn’t be a deterrent if it were readily bypassed.

You’ll need the Apple ID and password holding the lock, or the oriignal purchase receipt and matching ID and a discussion directly with Apple. As those are likely not options here, ask for a refund, assuming the seller hasn’t disappeared, and the seller can’t themselves recover their password.

This device is useless to you, otherwise.

The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community

Chat with the police if that is an option for you, but you’ll likely end up recycling this.

There is no way that it is going to get unlocked until the original owner unlocks it. I'm a little curious as to how it was working till all the sudden. Either way, it's not going to get unlocked without the Apple ID that it was signed up for that has it locked, unlocking it.