Hey, are you sure you're using the latest version of Lay Theme?
So basically, for product pages on mobile, we always had a carousel. There was no way to not have a carousel there. that was the default, and there was no setting to have it any other way.
Now you do have a setting to just have the images on top of each other in customize > woo commerce > single product page.
To me, it seems like you didn't activate the option that I told you about in my second answer post here:
http://laythemeforum.com:4567/topic/10972/woo-commerce-product-attributes-and-phone-carousel-missing/2
Another issue might be that you have a caching plugin and it's cached some things, so it doesn't work.
When I look at your page, I see on desktop you have no carousel and on mobile you have a carousel.
Well, I'm not even sure if I understand the issue cause u said:
On the phone layout, I use to have a carousel to display product images but now it doesn't work anymore and only display one picture.
You do have a carousel on mobile, so I'm not sure if I understand what the problem is.