The app is not authorized to use Firebase Authentication when published on the Play Store

I was using phone authentication for signing into my app. Everything worked perfectly fine during debugging and in the release version as well. However, upon publishing the app on the Play Store and during closed testing, testers reported an issue. They couldn’t sign in using their phone numbers and encountered an error message stating ‘App not authorized’

This issue indicated that Firebase didn’t recognized the app with the package name and sha-1 from the signed app that we have published.

After searching for a solution to this problem and trying different approaches, I finally found the correct solution.

To resolve the ‘not authorized’ app issue, you need to follow these steps precisely :

1-Find SHA1 and SHA-256 BOTH the certificate fingerprints from the play store console.

Play store Console > Your project > Setup > App signing

• Place BOTH SHA1 and SHA-256 fingerprints to your firebase app one by one.

Firebase Console > Your project > Settings of the app > Add Fingerprint

2-Verify if the package name in your Firebase project matches the one specified in the google-services.json file

"client_info": {
        "mobilesdk_app_id": "",
        "android_client_info": {
          "package_name": "com.example.projectname" // here must be the same with your fire base project package name
        }
      },

Now, with the issue resolved, your testers will be able to sign in without any problems.