The Apple iPhone 7 Plus has anti-theft and may affect how you are able to master reset the device. To use anti-theft, follow these steps:
- On the Home screen, tap Settings.
- Tap your Apple ID at the top of the list.
- Tap on your device from the list at the bottom.
- Tap Find My iPhone.
- Tap the slider next to Find My iPhone to enable or disable.
- Enter you Apple ID password and tap Turn Off.