yii2-adldap does not authenticate AD users

I am trying to login using yii2-adldap module but I am getting "Wrong password error". The password is correct. Here is my code:

  public function validatePassword($attribute, $params)
{

    if (!$this->hasErrors()) {
        $user = $this->getUser();
        if (!$user) {
            $this->addError('username', 'Incorrect username.');
        } else {
            $userprincipalname = $this->_user->queryLdapUserObject()->getAttribute('userprincipalname');

            if(! Yii::$app->ad->auth()->attempt($userprincipalname[0], $this->password)){

                $this->addError('password', 'Incorrect password.');
            }
        }
    }
}

And my getUser is below:

 public function getUser()
{
    if ($this->_user === false) {
        $this->_user = \Edvlerblog\Adldap2\model\UserDbLdap::findByUsername($this->username);
    }

    return $this->_user;
}

I should have seen this. After testing with a different Active Directory I found out that the problem has to do with how my AD is setup. Reverted my code to this and it worked (for some users):

   public function validatePassword($attribute, $params)
{


    if (!$this->hasErrors()) {
        $user = $this->getUser();

        if (!$user || !$user->validatePassword($this->password)) {
            $this->addError($attribute, 'Incorrect username or password.');
        }
    }

}

So I need to work with my System Administrator. Thank you.