Connect your device to iTunes again and create a new encrypted backup.It also removes your encrypted backup password. This won't affect your user data or passwords, but it will reset settings like display brightness, Home screen layout, and wallpaper.

Follow the steps to reset your settings.

Tap Reset All Settings and enter your iOS passcode.

On your iOS device, go to Settings > General > Reset.

Quoting from the Apple support page linked above: With iOS 11, Apple introduced a very simple way to reset your backup password. Backup encryption is a very important Apple security feature that thankfully we cannot bypass. Without your backup password, you will still be able to backup your device, but not browse the contents of your backups or restore them. The following Apple support entry is specifically dedicated to backup encryption, and covers lost passwords too: Because of this, if you set a backup password in iTunes, and later back up with iMazing, your iMazing backup will be encrypted with the same password as your iTunes backup, and vice versa. It will then be used to encrypt ALL future local backups of the device. The backup encryption password is set per device and is stored on the device itself.

This password is specific: it can be different from your device's passcode, which unlocks your device, or your Apple ID password. In order to access data in a backup, or to restore a backup to another device, you may be prompted to enter your backup password. Both iMazing and iTunes give you the option to encrypt your device's local backups.

Apple password to unlock iphone backup