A couple of questions for clarification:
Ok thank you for the clarification @Zeek
The banner on your site would not be controlled by the existence or absence of the discount code itself. The banner would be controlled by whatever app you are using to show banners on your store (unless the banner is an image and/or text that you have inserted in a section in your theme). The banner will continue to display until you disable or delete it from the app, or remove the image or text section you have inserted in your theme.
Are you the same person, but with a new username? Sorry for my confusion.
If a discount is being applied at checkout on your store, then it is still active in the 'Discounts' menu in your admin. That is the only way a discount will work on your site.