Erro no Login

Onde pode estar o erro?

Additional information: Zend\ServiceManager\Exception\ServiceNotCreatedException File: C:\sistemas\Estoque\Skeleton-Application\vendor\zendframework\zendframework\library\Zend\ServiceManager\ServiceManager.php:946 Message: An exception was raised while creating "Zend\Authentication\AuthenticationService"; no instance returned

UsuarioController.php

''' <?php namespace Estoque\Controller;

use Zend\Mvc\Controller\AbstractActionController;
use Zend\View\Model\ViewModel;

class UsuarioController extends AbstractActionController{

    public function indexAction(){

        return new ViewModel();
    }

    public function logoutAction(){
        $authService = $this->getServiceLocator()->get('Zend\Authentication\AuthenticationService');

        $authService->clearIdentity();

        return $this->redirect()->toUrl('/Usuario/Index');
    }

    public function loginAction(){

        if($this->request->isPost()){

            $dados = $this->request->getPost();

            $authService = $this->getServiceLocator()->get('Zend\Authentication\AuthenticationService');

            $authAdapter = $authService->getAdapter();

            $authAdapter­->setIdentityValue($dados['email']);
            $authAdapter­->setCredentialValue($dados['senha']);

            $authResult = $authService->authenticate();

            if($authResult­->isValid()) {
                return $this->redirect()->toUrl('/Index/cadastrar');
            }

            $this­->flashMessenger()-­>addErrorMessage("Login ou senha inválidos");

            return $this->redirect()->toUrl('/Usuario/index');

        }else{
            return $this->redirect()->toUrl('/Usuario/index');
        }
    }
}

?> '''