Have you tried log in as Password Forgot and it will ask you to enter the email address so, it can send you the password...........

   That will work if he's able to access the old owners E-mail to retrieve the password. Call the Autel support of your country with the unit serial number and register password found in "about"and let them know you bought the device second hand and want to put registration in your name and have the old owners email removed from unit as the primary email and  synch account and replaced with your own email.