Product Thumbnail Images issue on 3.3

Hello,

after updating to 3.3.1, my single product page renders original images in its original size instead of its related product thumbnail images. I am using Storefront and this is the source code that I get:

WooCommerce 3.2.6
<img src="image-120x120.jpg" class="flex-active" draggable="false">

WooCommerce 3.3.1
<img src="image.jpg" class="flex-active" draggable="false">

I have set up the new image sizes:

add_filter( 'storefront_woocommerce_args', 'image_settings' );

function image_settings( $args ) {
    $args['thumbnail_image_width'] = 300;
    $args['single_image_width'] = 600;
    return $args; 
}

But my product thumbnail images in my storefront child theme are neither 600px nor 300px. They are 1500px!

And this is the code in the official Storefront demo website:

<img src="canon-5d-mkiv-front.jpg?w=200&h=200&crop=1" draggable="false" class="flex-active" scale="0">

This is their image URL with the parameters:

https://demo.woothemes.com/storefront/wp-content/uploads/sites/78/2016/09/canon-5d-mkiv-front.jpg?w=200&h=200&crop=1

You can check it here:
https://demo.woothemes.com/storefront/product/build-your-dslr/

So these are my questions:

1. Why my Storefront theme is not rendering my product thumbnails images, and it is rendering the original images instead?

2. How the Storefront demo can resize images using parameters? Why these parameters are missing in my Storefront installation?

Thank you.