Mdm

You labeled the issue as MDM. If the iPad was a managed device you'll have to have the institution managing the device release it from management and remove the activation lock/account to which the device is tied.

Sounds like someone sold a company or school owned device online without having the deployment administrator release the device for private sale. If that is so, they may not have even owned and had the right to sell that device. Either way, you cannot do anything about it. Only the IT admin of the deployment can remove those restrictions on that device.