Your iPhone settings may have been automatically overwritten by the latest iOS version, resulting in an error. You may fix it by restoring your iPhone's settings to their original or default settings. This may be accomplished by resetting the system settings on your iPhone 7 Plus. Here's how to do it:

1. From the Home screen, choose Settings.
2. Select General.
3. Reset may be found by scrolling down and tapping it.
4. From the list of options, choose Reset All Settings.
5. To proceed, enter your passcode if required.
6. Then press the option to approve the reset of all settings.