Fixed this app is not allowed by the device owner

This error would appear if you accidentally switched the phone's user to a guest user. You also logged out of your Google account.

Symptoms

• Unable to text or make calls
• Hidden or missing Apps such as Facebook, WhatsApp, And X.
• Error "This app is not allowed for this device owner" 
• Error "This app is not allowed by the device owner" 
• Error "This app is not authorized by the device owner" 
• Error "This app has not been authorized by the device owner"

How to fix this Error?

If you receive these errors, Force Reboot your phone and you should be able to text and call, and hidden Apps will appear.

Note: to reboot your device you should press and hold your power button until you are presented with options to restart your device.