Not functioning when changing the quantity on the cart page.

Hello,

I’m trying to set a bulk discount on my site(with the oceanWP theme).
I could set the discount like this.
The conditions are different discount amounts based on the item quantity: (3~5 / 6~9 / 10~14 / 15~)

And when I add some of the discountable amounts from the product detail page, it works fine.
However, if I change the quantity on the cart page, it doesn’t reflect the changed discount condition.

Please advise how to approach to solve this issue.

Thanks,

P.s. And is there a shortcode or any method to show the discount condition on the product detail page?

The page I need help with: [log in to see the link]