Phalcon\Mvc\Micro\Exception: Not-Found handler is not callable or is not defined

<?php
 
declare(strict_types=1);
 
namespace Niden\Bootstrap;
 
use function Niden\Core\appPath;
use Phalcon\Di\FactoryDefault;
use Phalcon\Mvc\Micro;
 
/**
 * Class Api
 *
 * @package Niden\Bootstrap
 *
 * @property Micro $application
 */
class Api extends AbstractBootstrap
{
    /**
     * Run the application
     *
     * @return mixed
     */
    public function run()
    {
        return $this->application->handle();
    }
 
    /**
     * @return mixed
     */
    public function setup()
    {
        $this->container = new FactoryDefault();
        $this->providers = require appPath('api/config/providers.php');
 
        parent::setup();
    }
}

<?php
 
use Niden\Bootstrap\Api;
 
error_reporting(E_ALL); 
ini_set("display_errors", 1); 
 
function cors() {
  
  // Allow from any origin
  if (isset($_SERVER['HTTP_ORIGIN'])) {
    // Decide if the origin in $_SERVER['HTTP_ORIGIN'] is one
    // you want to allow, and if so:
    header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
    header('Access-Control-Allow-Credentials: true');
    header('Access-Control-Max-Age: 86400');    // cache for 1 day
  }
  
  // Access-Control headers are received during OPTIONS requests
  if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
  
    if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
        // may also be using PUT, PATCH, HEAD etc
        header("Access-Control-Allow-Methods: GET, POST, OPTIONS");         
  
    if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
        header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
  
    exit(0);
  }
  
}
 
cors();
 
$debug = new \Phalcon\Debug();
$debug->listen();
 
require_once __DIR__ . '/../../library/Core/autoload.php';
 
$bootstrap = new Api();
 
$bootstrap->setup();
$bootstrap->run();