Featured Image doesn't display in Preview ??

Hi,
Thank you for that extremely helpful plugin!
I’m building a WooCommerce website (WordPress), and I used your plugin on one product to try it:
I uploaded the Featured image on Imgur, and put the URL of the image.
The image shows in the Thumbnail, and in the Product Page normally.
However, when you click on it to preview a bigger size… it doesn’t load!

Here is the URL of the Product: http://vapingchannel.com/product/aspire-premium-starter-kit/
Here is the URL of the image: http://i.imgur.com/22YX3am.jpg

I hope that you could point me to the right direction,
Thank you!

https://wordpress.org/plugins/external-featured-image/