After a user clicks on the Decline button, the notification bar is not displayed again

Of course, it should not be displayed again if the user has already clicked on the Decline button.

The shortcode functionality exists for this situation. You can put the shortcode text {cookiesinfo} in your cookies policy content item, or inside a module, and the user will be able to reconsider and changes his first decision, as you can see in the below screenshot.

Screenshot of the shortcode cookies info table after the user has clicked on the Decline button