Micro App , Routing doesn't match

when i run those code

<?php

use Phalcon\Mvc\Micro;

$app = new Micro();

$app->get(
    '/orders/display/{name}',
    function ($name) {
        echo "<h1>This is order: {$name}!</h1>";
    }
);

$app->handle();

when i try to visit "/orders/display/hello" error occurred

Fatal error: Uncaught Phalcon\Mvc\Micro\Exception: Not-Found handler is not callable or is not defined in /home/vagrant/test-phalcon/index.php:14 Stack trace: #0 /home/vagrant/test-phalcon/index.php(14): Phalcon\Mvc\Micro->handle() #1 {main} thrown in /home/vagrant/test-phalcon/index.php on line 14

so i add some code like this

$app->notFound(
    function () use ($app) {
        $app->response->setStatusCode(404, 'Not Found');
        $app->response->sendHeaders();

        $message = 'Nothing to see here. Move along....';
        $app->response->setContent($message);
        $app->response->send();
    }
);

Try to visit "/orders/display/hello", then the page display

Nothing to see here. Move along....

I consider it should display

<h1>This is order: hello!</h1>

is anyone know how to solved this problem, thanks.