Facebook Messenger Generic template not showing

I am using Botman Studio to build a Facebook Messenger bot but I can't get the Generic template to show. It returns a blank message. I am following this docs - https://botman.io/2.0/driver-facebook-messenger and this is what I am doing. I don't know the problem might be

$discos = DB::select("select * from discos where status = 1");
    foreach ($discos as $disco){
        $res[] = array(
            Element::create($disco->title)
                ->subtitle($disco->sub_title)
                ->image($disco->img_url)
                ->addButton(ElementButton::create('Pay')->payload($disco->slug)->type('postback'))

        );
    }
$bot->reply(GenericTemplate::create()
        ->addImageAspectRatio(GenericTemplate::RATIO_SQUARE)
        ->addElements($res)
    );

via Chebli Mohamed