Changed Firebase Project, it gives me error [ API key not valid. Please pass a valid API key. ] during Authentication

Question

I changed my flutter app's backend firebase project, deleted the previous firebase project and put other firebase project's google-services.json file in my app (with the required build.gradle changes in project-level and app-level).

Now, when I use the Firebase Auth (email and password method), it throws this error in debug console.

I/flutter (15914): PlatformException(FirebaseException, An internal error has occurred. [ API key not valid. Please pass a valid API key. ], null)

Before deleting the previous Firebase Project, everything was working fine, but then when I changed it to other Firebase Project, it threw this error. How do I fix it?

Solution

In this case, please clean and rebuild again and it should work.

Commands:

flutter clean 
flutter run / build