ошибка во время аутентификации firebase

Question

я работаю над приложением чата и мне нужно дать логин и создать бесплатную учетную запись с помощью firebase ... я пытался, но у меня возникли некоторые проблемы, связанные с этим ... я не могу перейти к другому экрану, т.е. к основной деятельности после созданиявместо этого в новой учетной записи отображается всплывающее предложение "Вы получили какую-то ошибку" ..

RegisterActivity.java

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.design.widget.TextInputLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

public class RegisterActivity extends AppCompatActivity {
    private TextInputLayout mDisplayName;
    private TextInputLayout mEmail;
    private TextInputLayout mPassword;
    private Button mcreateBtn;
    private FirebaseAuth mAuth;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);

        mAuth = FirebaseAuth.getInstance();


        mDisplayName =(TextInputLayout)findViewById(R.id.reg_display_name);
        mEmail = (TextInputLayout)findViewById(R.id.reg_email);
        mPassword=(TextInputLayout) findViewById(R.id.reg_password);
        mcreateBtn = (Button) findViewById(R.id.reg_create_btn);

        mcreateBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String display_name = mDisplayName.getEditText().getText().toString().trim();
                String email = mEmail.getEditText().getText().toString().trim();
                String password = mPassword.getEditText().getText().toString().trim();

                register_user(display_name, email, password);

            }
        });




    }

    private void register_user( String display_name, String email, String password) {
        mAuth.createUserWithEmailAndPassword(email, password).addOnCompleteListener( new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                           Intent mainIntent = new Intent(RegisterActivity.this,MainActivity.class);
                           startActivity(mainIntent);
                           finish();
                        } else {
                            Toast.makeText(RegisterActivity.this,"you got some error.",Toast.LENGTH_LONG).show();
                        }

                        // ...
                    }
                });
    }
}

activity_Register.xml

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".RegisterActivity">

    <android.support.design.widget.TextInputLayout
        android:id="@+id/reg_display_name"
        android:layout_width="368dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="40dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <android.support.design.widget.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/display_name" />
    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/reg_email"
        android:layout_width="368dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/reg_display_name">

        <android.support.design.widget.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/e_mail" />
    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/reg_password"
        android:layout_width="368dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/reg_email">

        <android.support.design.widget.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/password" />
    </android.support.design.widget.TextInputLayout>

    <Button
        android:id="@+id/reg_create_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="Create Account"
        app:layout_constraintTop_toBottomOf="@+id/reg_password"
        tools:layout_editor_absoluteX="212dp" />
</android.support.constraint.ConstraintLayout>