为什么Firebase signInWithEmailAndPassword（）身份验证对我不起作用？

Question

login(email,password)函数似乎有一个我不知道的问题。 task.isSuccessful()始终失败。这是代码：

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.snackbar.Snackbar;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.uptoplegendary.blog.R;

public class MainActivity extends AppCompatActivity {

    private EditText emailField;
    private EditText passwordField;
    private Button loginBtn;
    private Button createAccBtn;

    //private FirebaseUser mUser;
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        emailField = (EditText) findViewById(R.id.loginEmailID);
        passwordField = (EditText) findViewById(R.id.loginPasswordID);
        loginBtn = (Button) findViewById(R.id.loginBtn);
        createAccBtn = (Button) findViewById(R.id.createAccBtn);

        mAuth = FirebaseAuth.getInstance();

        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {

                FirebaseUser mUser = firebaseAuth.getCurrentUser();

                if (mUser != null) {

                    Toast.makeText(MainActivity.this, "Signed in!", Toast.LENGTH_LONG).show();

                    startActivity(new Intent(MainActivity.this, PostListActivity.class));
                }
                else {

                    Toast.makeText(MainActivity.this, "Signed out!", Toast.LENGTH_LONG).show();
                }
            }
        };

        loginBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String email = emailField.getText().toString();
                String pwd = passwordField.getText().toString();

                if (!TextUtils.isEmpty(email) && !TextUtils.isEmpty(pwd)) {

                    login(email, pwd);
                }
                else {

                    Snackbar.make(v, "Enter valid email and password", Snackbar.LENGTH_LONG).show();
                }
            }
        });
    }

    private void login(String email, String pwd) {

        mAuth.signInWithEmailAndPassword(email, pwd)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {

                            Toast.makeText(MainActivity.this, "Signed in!",
                                    Toast.LENGTH_SHORT).show();
                        } else {
                            // If sign in fails, display a message to the user.
                            Toast.makeText(MainActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        }

                        // ...
                    }
                });
    }

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {

        if (item.getItemId() == R.id.action_signout) {

            mAuth.signOut();
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.main_menu, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    protected void onStart() {

        super.onStart();
        mAuth.addAuthStateListener(mAuthListener);
    }

    @Override
    protected void onStop() {
        super.onStop();

        if (mAuthListener != null) {

            mAuth.removeAuthStateListener(mAuthListener);
        }
    }
}