If the customer misses to use shipping calculation

Ok here is the question;

An international customer adds the item to the cart but forgets to calculate shipping and moves to the checkout process. Then, no shipping cost shows up even the shipping country is selected at the checkout page and lets the customer to check out with only the products amount with no shipping.

But if s/he clicks on calculate shipping at the cart page and selects his country and moves to the checkout process this time shipping cost shows up and added to the order total.

So, any idea?

https://wordpress.org/plugins/oik-weightcountry-shipping/