To resolve the issue of the google-services.json file not updating with the new SHA-1 fingerprint, ensure that at least one sign-in authentication method is enabled in Firebase Authentication settings. Follow the steps below:

Access Firebase Console:

Navigate to the Firebase Console. Select your project. Enable a Sign-In Authentication Provider:

Go to Build -> Authentication -> Sign-in method tab. Enable at least one authentication provider, such as Email/Password or Google Sign-In. Save the changes. Re-download google-services.json:

Go to Project Settings -> Your apps -> Android App. Download the updated google-services.json file. Replace the existing file in your Flutter project (android/app/ directory).