Reset it to factory settings (see, Settings – personal – backup, Reset – ZTE Grand X Plus User Manual
Page 163: You need to do some settings before using it, Accounts, System, Backup and reset, Accessibility
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Backup and Reset
• Back up my data: Back up app data, Wi-Fi passwords, and
other settings to Google servers after you sign in to your
Google account.
• Back up account: Set the Google account that the data is
backed up to.
• Automatic restore: Restore previously backed up settings
and data when you reinstall an app.
• Factory data reset: Reset your phone to factory default
settings. All your personal data from the phone’s internal
storage will be erased. You can also erase the data on the
microSDHC card during the process.
Accounts
Manage your accounts and synchronization. Touch Add
account to sign in to or create accounts on your phone.
Touch an account type to see that type of accounts you have
added and adjust the accounts settings.
System
Accessibility
Configure accessibility plug-ins on your phone, such as using
TalkBack for low-vision users.