Форма входа Symfony 3.4 всегда возвращает «неверные учетные данные»

Я изо всех сил пытаюсь заставить работать форму входа Symfony (версия 3.4).
Он всегда возвращает «Неверные учетные данные», когда я пытаюсь войти в систему.
Тестовый пользователь (с зашифрованным паролем) уже сохранен в базе данных MySql.

Я просто следовал примеру документации, которую можно найти Вот.

Это файл security.yml:

# To get started with security, check out the documentation:
# https://symfony.com/doc/current/security.html
security:
encoders:
AppBundle\Entity\User:
algorithm: bcrypt

# https://symfony.com/doc/current/security.html#b-configuring-how-users-are-loaded
providers:
our_db_provider:
entity:
class: AppBundle:User
property: username

firewalls:
# disables authentication for assets and the profiler, adapt it according to your needs
dev:
pattern: ^/(_(profiler|wdt)|css|images|js)/
security: false

main:
anonymous: ~
# activate different ways to authenticate

# https://symfony.com/doc/current/security.html#a-configuring-how-your-users-will-authenticate
pattern: ^/
http_basic: ~
provider: our_db_provider

# https://symfony.com/doc/current/security/form_login_setup.html
form_login:
login_path: login
check_path: login

Это сущность User.php:

<?php

// src/AppBundle/Entity/User.php
namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Validator\Constraints as Assert;
use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
use Symfony\Component\Security\Core\User\UserInterface;

/**
* @ORM\Table(name="app_users")
* @ORM\Entity(repositoryClass="AppBundle\Repository\UserRepository")
* @UniqueEntity(fields="email", message="Email already taken")
* @UniqueEntity(fields="username", message="Username already taken")
*/
class User implements UserInterface, \Serializable
{
/**
* @ORM\Column(type="integer")
* @ORM\Id
* @ORM\GeneratedValue(strategy="AUTO")
*/
private $id;

/**
* @ORM\Column(type="string", length=25, unique=true)
*/
private $username;

/**
* @ORM\Column(type="string", length=64)
*/
private $password;

/**
* @Assert\NotBlank()
* @Assert\Length(max=4096)
*/
private $plainPassword;

/**
* @ORM\Column(type="string", length=60, unique=true)
*/
private $email;

/**
* @ORM\Column(name="is_active", type="boolean")
*/
private $isActive;

public function __construct()
{
$this->isActive = true;
// may not be needed, see section on salt below
// $this->salt = md5(uniqid('', true));
}

public function getUsername()
{
return $this->username;
}

public function setUsername($username)
{
$this->username = $username;

return $this;
}public function getSalt()
{
// you *may* need a real salt depending on your encoder
// see section on salt below
return null;
}

public function getPassword()
{
return $this->password;
}

public function setPassword($password)
{
$this->password = $password;

return $this;
}

public function getPlainPassword()
{
return $this->plainPassword;
}

public function setPlainPassword($password)
{
$this->plainPassword = $password;

return $this;
}

public function getEmail()
{
return $this->email;
}

public function setEmail($email)
{
$this->email = $email;

return $this;
}

public function getRoles()
{
return array('ROLE_USER');
}

public function eraseCredentials()
{
}

/** @see \Serializable::serialize() */
public function serialize()
{
return serialize(array(
$this->id,
$this->username,
$this->password,
// see section on salt below
// $this->salt,
));
}

/** @see \Serializable::unserialize() */
public function unserialize($serialized)
{
list (
$this->id,
$this->username,
$this->password,
// see section on salt below
// $this->salt
) = unserialize($serialized);
}

}

Это контроллер:

<?php

// src/AppBundle/Controller/SecurityController.php
namespace AppBundle\Controller;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Security\Http\Authentication\AuthenticationUtils;
use Symfony\Component\Routing\Annotation\Route;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;

class SecurityController extends Controller
{

/**
* @Route("/login", name="login")
*/
public function loginAction(Request $request, AuthenticationUtils $authUtils)
{
// get the login error if there is one
$error = $authUtils->getLastAuthenticationError();

// last username entered by the user
$lastUsername = $authUtils->getLastUsername();

return $this->render('security/login.html.twig', array(
'last_username' => $lastUsername,
'error'         => $error,
));
}

}

И наконец, шаблон веточки:

{# app/Resources/views/security/login.html.twig #}

{% extends 'default.html.twig' %}

{% block pageTitle %} Login {% endblock %}

{% block pageStyle %} {{ parent() }} {% endblock %}

{% block pageScriptsHeader %} {{ parent() }} {% endblock %}

{% block navigation %} {{ parent() }} {% endblock %}

{% block mainContainer %}

{% if error %}
<div>{{ error.messageKey|trans(error.messageData, 'security') }}</div>
{% endif %}

<form action="{{ path('login') }}" method="post">
<div class="form-group">
<label for="username">Username:</label>
<input class="form-control" type="text" id="username" name="_username" value="{{ last_username }}" />
</div>

<div class="form-group">
<label for="password">Password:</label>
<input class="form-control" type="password" id="password" name="_password" />
</div>

{#
If you want to control the URL the user
is redirected to on success (more details below)
<input type="hidden" name="_target_path" value="/account" />
#}

<button type="submit" class="btn btn-primary">login</button>
</form>{% endblock %}

Я полагаю, что проблема связана с паролем. Может быть не зашифровано перед сравнением с базой данных?

Любая помощь будет оценена.