Hello, @slw250@hotmail.com,
Actually, on the shop page, there is no option in the theme to show this as you can see in the image only this content will be available to show: https://postimg.cc/y3kYkbRR
On the single product page, I edit a product and set the GTIN in it and when I check it appears just fine to check the images for a better reference: https://postimg.cc/z3RsGNbj and https://postimg.cc/WFZ5T2Wq please check back to your site after clearing the browser cache.
Regards 8Themes Team.