Problem with $_SESSION in PHP: array(0) { } before storing user data

I'm trying to authenticate a user and store the data in the session. I expected that the session should contain the user's data after login, but the current behaviour is that var_dump($_SESSION) displays array(0) { } before displaying the correct data.

The functions used are

public function autenticar($email, $senha) {
        $usuario = $this->model->buscarPorEmail($email);
        if ($usuario && $this->model->validarSenha($email, $senha)) {
            $_SESSION['usuario'] = [
                'id' => $usuario['id'],
                'nome' => $usuario['nome'],
                'email' => $usuario['email'],
                'tipo' => $usuario['tipo']
            ];
            return true;
        }
        return false;
    }

public function login() {
        if ($_SERVER['REQUEST_METHOD'] === 'POST') {
            $email = $_POST['email'] ?? null;
            $senha = $_POST['senha'] ?? null;
            if ($this->autenticar($email, $senha)) {
                var_dump($this->autenticar($email, $senha));
                header('Location: /sebo/public/');
                exit;
            } else {
                echo $this->twig->render('/login.twig', [
                    'error' => 'E-mail ou senha inválidos.'
                ]);
            }
        } else {
            echo $this->twig->render('/login.twig');
        }
    }