PlayGamesClientConfiguration config = new PlayGamesClientConfiguration.Builder()
     .AddOauthScope("profile")
     .RequestServerAuthCode(false)
     .Build();
 
 PlayGamesPlatform.InitializeInstance(config);
 // recommended for debugging:
 PlayGamesPlatform.DebugLogEnabled = true;
 // Activate the Google Play Games platform
 PlayGamesPlatform.Activate();
 
 // authenticate user:
 PlayGamesPlatform.Instance.Authenticate(SignInInteractivity.CanPromptOnce, (SignInStatus result) => {
     if (result == SignInStatus.Success)
     {
         Debug.Log("Authentication Succeeded.");
     }
     else
     {
         Debug.Log("Authentication Failed. SignInStatus: " + result);
     }
 });

 public void PlayFabLoginWithGoogleAccount()
 {
     var serverAuthCode = PlayGamesPlatform.Instance.GetServerAuthCode();

     var request = new LoginWithGoogleAccountRequest
     {
         ServerAuthCode = serverAuthCode,
         TitleId = PlayFabSettings.TitleId
     };
 
     PlayFabClientAPI.LoginWithGoogleAccount(request, OnLoginWithGoogleAccountSuccess, OnLoginWithGoogleAccountFailure);
 }

 private void OnLoginWithGoogleAccountSuccess(LoginResult result)
 {
     Debug.Log("PlayFab LoginWithGoogleAccount Success.");
 }

 private void OnLoginWithGoogleAccountFailure(PlayFabError error)
 {
     Debug.Log("PlayFab LoginWithGoogleAccount Failure: " + error.GenerateErrorReport());
 }

public void LinkGooglePlayGamesAccount()
{
   PlayGamesPlatform.Instance.GetAnotherServerAuthCode(true, (serverAuthCode) => {

       var linkRequest = new LinkGooglePlayGamesServicesAccountRequest
       {
           ServerAuthCode = serverAuthCode
       };

       PlayFabClientAPI.LinkGooglePlayGamesServicesAccount(linkRequest, OnLinkGooglePlayGamesServicesAccountSuccess, OnLinkGooglePlayGamesServicesAccountFailure);
   });
}

private void OnLinkGooglePlayGamesServicesAccountSuccess(LinkGooglePlayGamesServicesAccountResult result)
{
   Debug.Log("PlayFab LinkGooglePlayGamesServicesAccount Success");
}

private void OnLinkGooglePlayGamesServicesAccountFailure(PlayFabError error)
{
   Debug.Log("PlayFab LinkGooglePlayGamesServicesAccount Failure: " + error.GenerateErrorReport());
}

 public void PFLoginWithGooglePlayGames()
 {
     PlayGamesPlatform.Instance.GetAnotherServerAuthCode(true, (serverAuthCode) => {

         var request = new LoginWithGooglePlayGamesServicesRequest
         {
             ServerAuthCode = serverAuthCode,
             CreateAccount = false,
             TitleId = PlayFabSettings.TitleId
         };
 
         PlayFabClientAPI.LoginWithGooglePlayGamesServices(request, OnLoginWithGooglePlayGamesServicesSuccess, OnLoginWithGooglePlayGamesServicesFailure);
     });
 }

 private void OnLoginWithGooglePlayGamesServicesSuccess(LoginResult result)
 {
     Debug.Log("PlayFab LoginWithGooglePlayGamesServices Success.");
 }

 private void OnLoginWithGooglePlayGamesServicesFailure(PlayFabError error)
 {
     Debug.Log("PlayFab LoginWithGooglePlayGamesServices Failure: " + error.GenerateErrorReport());
 }

 public void UnlinkGoogleAccountFromPlayer()
 {
     PlayFabClientAPI.UnlinkGoogleAccount(new UnlinkGoogleAccountRequest(), OnUnlinkGoogleAccountSuccess, OnUnlinkGoogleAccountFailure);
 }
 
 private void OnUnlinkGoogleAccountSuccess(UnlinkGoogleAccountResult result)
 {
     Debug.Log("PlayFab UnlinkGoogleAccount Success.");
 }
 
 private void OnUnlinkGoogleAccountFailure(PlayFabError error)
 {
     Debug.Log("PlayFab UnlinkGoogleAccount Failure: " + error.GenerateErrorReport());
 }