 To reset Google account activation or Samsung reactivation lock:
1. Power on phone in download mode (turn off phone, press vol.down + home + power).
2. Connect phone to PC with USB cable, install drivers if needed.
3. Press "Reset FRP/React/EE" to deactivate Google/Samsung/EE account activation lock.
  (Sometimes needs to perform "wipe data/factory reset" once more, to complete this locks removal.)