Missing preview images for products in WooCommerce. How to restore and why disappeared?

Question

Gallery

Suddenly, all the preview pictures in the product cards disappeared.
Those. the field where the picture is, by clicking on the area - a full-size picture opens, but there are no previews in the product cards, neither the main image of the product, nor the gallery.
How to fix?

Answer 1

Woocommerce updated? in the 3rd version, a new product gallery. The image appears when the page loads. See errors in the console. Maybe jQuery is faking it. Is there a picture in the markup? and 404 does not issue a thumbnail for download?
UPD. One of the woocommerce scripts does not work for you, which makes the gallery opaque.
Perhaps the built-in woomers scripts are disabled in the functions.php of the theme.
Style this block with opacity:1!important;

Answer 2

How to fix?

If everything is fine with the hosting and the pictures are uploaded to the media library, but "disappeared" - physically, then https://wordpress.org/plugins/regenerate-thumbnails/ will help

Answer 3

Woocommerce 3.0.6, by the way, may have glitched after the update...
There is a markup, but there is no 404.
"Errors in the console" - where is this? Consoles of all WordPress? I don't see or don't know where to look.