Does not add shipping cost to total

I have not set up any special shipping classes. I’ve simply set it up to ship flat rate to UK, but my cart does not display my shipping costs or add it to the total.

It just says “flat rate’ or whatever I edit the name of the shipping to.

See here for example https://www.artbecomesyou.com/product/zara-black-leather-high-heel-ankle-boots/

So frustrating. Please help. I’ve watched endless tutorials, read so many forums and tried several ways around it with no results.