Featured Image doesn't show on the Product page – WordPress

I’m struggling with my wordpress page, with woocommerce. The featured image should be showing as the first image on the product page, but isn’t. I’ve read a few other threads, like this one:

Product Images don't show (Woocommerce)
where they have some solutions, but the CSS they are proposing isn’t working.

My page is here: www.byjgk.com , and for example, if you check out a product category page, like: https://www.byjgk.com/product-category/dresses/ , and then select a dress (e.g.: https://www.byjgk.com/product/the-jersey-maxi-dress-petite-in-sandstone/), you should then see the same featured which was on the category page also appear as the first image on the product page as WELL/(in addition to the other 3 images that are there).

Normally, that’s how the image feature works, so there must be some opacity/other problem.

I also did try changing the woocommerce.css file, (which was also a suggestion in the link above, to put this there:

.product.has-default-attributes.has-children > .images{opacity :1;}

but i didn’t see any class called exactly that with the word "children".

I also tried to put the "jquery" that was suggested:

$(‘.woocommerce-product-gallery–with-images’).css(‘opacity’, 1);

into the functions.php section, but it said this query had some sort of error, or it didn’t like the "$" maybe…

Soooo, I’m at a loss. please help. I see a few people have asked about this on some other forums, but many don’t figure it out.

thanks!