Activation lock

Bought a Mac mini of someone online, made sure they logged out of iCloud when I went to pickup. Did not realise that find my is still logged in when you log out of iCloud. I am now locked behind the activation lock, and the device password is not being allowed to bypass it. It insists on the AppleId of the owners who’s slowed his responses since he already got payed and naturally isn’t comfortable sharing his password. The device isn’t on his iCloud or anything anymore, is there anything I can do to lift this activation lock?