Why Facebook application id suddenly become invalid?

Question

First of all I'm sure that my fb app id is valid because users can log in my Android app using facebook credentials until some days ago (I think it's before Feb break change).

Recently new users cannot log in my Android app using facebook any more because facebook keep saying that my fb app invalid (Error is: Invalid application fb-app-id) BUT old users who already authorized my Android app for accessing their info can still log in using facebook. (Old users can still login to my app using facebook credentials but new users cannot)

Does anyone know why this happen to my facebook app and how to fix it?

Edit: When access to https://graph.facebook.com/facebook-app-id I get this error

{
"error": {
  "message": "Unsupported get request.",
  "type": "GraphMethodException",
  "code": 100
    }
   }

Thanks you.

Answer 1

If you're sure the app is not in sandbox mode (which was gema.megantara's answer), and hasn't been deleted for policy reasons by Facebook the only explanation I can think of is that you've restricted the app demographically (i.e by country or age)

If that's the case the API won't return the app's details unless you make the API call using a user access token for a user who meets whatever restrictions you've applied, and users who don't meet the requirements won't be able to use the app.

If that's what you've done, you can remove the restrictions via the API (via the restrictions field of the Application object or in the ''Advanced'' tab in the app settings in the App Dashboard

If using the frontend interface to change the settings, it's the ''App Restrictions'' field you want to edit, screenshot attached