Twitter cards not showing image

Hi there!

I’m using your plugin and have it all set up so that Twitter displays an image on tweets, but it doesn’t.

I set the featured image to show on Twitter through the plugin’s box, but still my tweets have no image.

For example: https://dulcesdiabeticos.com/mona-chocolate-sin-azucar-pascua/

Este pastel de #chocolate y almendras no lleva azúcar y apenas harina… ?te encantará! https://t.co/11qEL2ZESv #recetas

— Dulces Diabéticos (@DulcesDiab) April 20, 2017

How can I solve this?

Thanks!