coupon function don't work on the customer checkout page

I encounter a problem when I generate a coupon code and assign to a customer, but coupon function didn't show up in this customer check out page, anyone can help me?

Hello,

To have a coupon automatically discounted, please follow these instructions:
https://awodev.com/blog/create-automatic-discount-awocoupon-pro

Hello Seyi,

I follow the instructions and success once, but now it don't work again! is it possible give you my url and backend access then help me figure out what happen?

Yes, please send me a private message with the information