It meens u have not define the conroller called IndexController or you didnt load the Controllers,you can put your publc/index.php code on the page when you reply,may be i can find the error
Just like this:
if you have defined namespce,you can
$loader = new \Phalcon\Loader();
    $loader->registerNamespaces(array(
        'Brand\Models'      => $config->application->modelsDir,
        'Brand\Plugins'     => $config->application->pluginsDir,
        'Brand\Library'     => $config->application->libraryDir
    ));
or not,you can
$loader->registerDirs(array(
     $config->application->controllersDir,
))
Becasue i have create more modules for my project,so u can choose a better way to solve your problem