Coupon Codes not being applied

Hi,
My customers are complaining that the coupons code discounts are not being applied to their orders. I have verified that is true. Below is a screenshot of my settings.
Thanks

Hello Dan,
To be able to use this Coupon, the sub total must reach $19. Also, please test by yourself if you are able to use this coupon or not.
Sincerely, Giang

Hi, I don't sell any items for less than $19. I have verified that the coupon code is not working. Also, is it necessary to set a start and end date? Can I leave those fields blank?

I am attaching a screenshot of the error that occurs when I am trying to use the coupon code.

Hello Dan,
I am sure that you made some wrong things in setting of that coupon code. Please submit a new ticket to EShop category to send me the back-end log-in account to your site so I can help you to check that.
Hope to receive your ticket soon.
Sincerely, Giang