Can't generate errors when using PFBC validation

Problem:

I have adopted the framework of PFBC in order to validate form elements but despite following (at least what I believe) every step to validate a form field it does not generate the error message.

Code:

<?php
    // Initialize session
    session_start();

    use PFBC\Form;
    use PFBC\Element;
    use PFBC\Validation;
    use PFBC\View;

    // Include PHP Form Builder Class
    require_once 'inc/PFBC/Form.php';

    // Include PHP PDO Wrapper Class
    require_once 'inc/class.db.php';

    // Define database configuration
    require_once 'inc/class.config.php';

    // Include header
    require_once 'inc/header.php';

    $form = new Form("validation");

    $form->configure(array(
        "prevent" => array("bootstrap", "jQuery", "focus")
    ));

    $form->addElement(new Element\Hidden("form", "validation"));
    $form->addElement(new Element\HTML('<legend>Title - <small>Subtitle</small></legend>'));
    $form->addElement(new Element\HTML('<p>Text</p>'));
    $form->addElement(new Element\Password("Enter code:", "Password", array(
        "validation" => new Validation\AlphaNumeric,
        "longDesc" => "The AlphaNumeric validation class will verify that the element's submitted value contains only letters, numbers, underscores, and/or hyphens.",
        "required" => 1
    )));
    $form->addElement(new Element\Button("Send"));
    $form->render();

    // Include footer
    require_once 'inc/footer.php';
?> 

Desired output:

An error message should be displayed if user left field empty.