Since Prestashop 1.7, the reference, EAN and availability are located on the product page at the bottom, in "Product details" tab. Compared to older versions, it is quite an inappropriate location. Unfortunately, it is not possible to move this data elsewhere in our templates by default, because in order to work properly including refreshing combinations (attributes), it requires also modifications of core files (outside the template).
If you need to move these data to another place (for example, the reference under the product heading and availability close to "add to cart" button), contact us and we will do it for you. For our themes we offer this service for better price.