Can I edit or cancel my sale ad after it’s already been published?
You can absolutely edit or cancel your sale ad after it's been published. The sale title, description, dates and times, address, photos, etc can all be changed very easily. Editing only becomes disabled once the sale has ended.
You can also "Unpublish" a sale after it's been published by clicking the "Unpublish sale" link directly underneath the Publish button on the "Options & Publish" screen for the sale, or by clicking the Edit icon to the right of the sale from your "Sales" tab and selecting "Unpublish Sale". Unpublishing a sale saves it in your Sales list as a "Saved Draft" where it is only visible to you.