You can leave your promotion date adjustable.
Discount your book more for the promotion.
If your book is low on reviews, wait until you have received more reviews on your book.
Check out other covers in your genre to see if your cover is as good or better. Ask others to give their opinion on the cover and what you can do to improve it.
Make sure your blurb doesn't have errors and is comparable to other books out there. Learn how to format them correctly on the different platforms.
Make sure your ebook doesn't have extra spacing between paragraphs. Make sure it is indented enough not to be confusing.
Have an editor read through your book again. Make sure your punctuation (commas, quotes, long dashes, etc.) are uniform. Even some books that have no typos sometimes need more content editing.