There is a known issue with facebook which prohibits 2 factor authentication setup with other apps if facebook mobile app is not setup.

Follow the below steps to add an account with Authenticator Plus

  1. Facebook security settings
  2. Code Generator Setup -> setup using facebook mobile app
  3. Set up another way to get security codes -> scan the QR code in Authenticator Plus
  4. now if you don’t need facebook app you can uninstall it