The denial of gigs is a feature that was added to Fiverr in 2014. In order to use this feature, you need to be logged in to your account and go to the My gigs page. From here, you can click on the Denied gigs link in the left-hand column. This will take you to a page where you can review the gigs that you have previously denied.
In order to approve or deny a gig, you will need to click on the green approve or deny button. If you want to cancel a denied gig, you will need to click on the red cancel button.