We are using the Venture theme. When adding a product to the cart, it says it was added. But if you go to the cart in any way the item isn't there.
Here is a link. And screenshot of the confirmation.
What can we do to fix this?
Are you able to add the theme again from the Shopify themes store?
You can add it into your shop's themes, but don't need to publish it. Just preview the theme and try adding items to the cart.