I have followed the tutorial here: https://developers.google.com/identity/sign-in/android/start-integrating to integrate Google sign in into my app.
However, the
The problem was that I was running the app from Android Studio (without setting up signingConfig), so the app wasn't signed with my certificate, which Google Sign-in requires.
If you run from Android studio without signingConfigs, then it is using your debug key store to sign. You can try register your package name + debug key SHA1 in dev console for easy development:
Test google signin on Android in development phase