I lost a few hours on this one, so let me share my experience on this.

Gms stands for "Google Mobile Services", and its basically an addon API to Android developed by Google that allows to connect to a bunch of Google-provided services. If you use flutter, this is probably wrapped by flutter packages you use such as firebase_auth, flutter_facebook_login or/and google_sign_in.

This error may sometimes be handled by the higher level components, so if you have that error, it doesn't mean your configuration is wrong or it won't work. In my case I had this error with successful end result when I was logging using Google Sign in, something like this:

info flutter.tools W/BiChannelGoogleApi( 4106): [FirebaseAuth: ] getGoogleApiForMethod() returned Gms: com.google.firebase.auth.api.internal.zzak@8116b2c
info flutter.tools D/FirebaseAuth( 4506): Notifying id token listeners about user ( lCZZZZJELWhGUZZZZB3vDklZZZZ2 ).
info flutter.tools D/FirebaseAuth( 4506): Notifying auth state listeners about user ( lCZZZZJELWhGUZZZZB3vDklZZZZ2 ).
info flutter.tools I/flutter ( 4506): FirebaseUser({uid: lCZZZZJELWhGUZZZZB3vDklZZZZ2, photoUrl: https://lh5.googleusercontent.com/-ZZzir_P-ENw/AAAAAAAAAAI/AAAAAAAAAAA/PpxhiXg_ISk/s96-c/photo.jpg, isAnonymous: false, etc....

I have a dart call print(fireUser); in my code so we see it's a success.

But in the case of Facebook Auth, I just had this, and nothing happened after that, but on the Facebook server side, login was succeeding as I could see events in Facebook dev console.

info flutter.tools W/BiChannelGoogleApi( 4106): [FirebaseAuth: ] getGoogleApiForMethod() returned Gms: com.google.firebase.auth.api.internal.zzak@8116b2c

And nothing else after in the log, so something was stuck in the process.

My problem was I mixed two applications App Id and Secret. I'm a bonehead sometimes, but the thing is there's zero warning or specific error nowhere, so here are a list of things that can fail with Firebase and other plugins:

• Make sure you have properly configured the sign-in provider (google, facebook, etc.) in Firebase console
• Upgrade all flutter packages. I personnaly don't use package versions, I use all flutter packages latest version. And I use AndroidX.

In the specific case of Facebook Auth (I find Google Sign In much easier to integrate):

• make sure your looking at the good app
• make sure the App ID and App secret are the good one. In Facebook dev console, check the Basic Settings there.
• make sure you have added the "Facebook Login" product. If you don't see it in the left menu, in Facebook dev console, check the Dashboard and add it.
• in the "Facebook Login" product settings, make sure you have added the "Valid OAuth Redirect URIs" that Firebase console gives you (in the Facebook Sign-in provider config). You can check it in the "Redirect URI validator" tool lower in that page.
• in the Basic Settings of the app, if you use flutter (=> mobile platforms), make sure you have an IOS section/platform and and Android section/platform. To achive that you can do it manually "Add platform", or use the Quick Starts.
• in the end, the IOS section can contain only the "Bundle ID"
• and the Android section should containe the "Google Play Package Name", the "Class Name" and at least one "Key Hashes" (for debug). If you don't know how to create the hash, use the "Facebook Login" quick start.

Hope this helps