I just successfully used the spring20 discount to buy a book.
You do have to watch after you press "apply" to see if the book price is correct and the discount has been applied. Some publishers do not allow their books to be discounted in this way. I have always gotten a warning by the applied box when the coupon is invalid for that book, or if the coupon has expired, etc.
You can open a web help ticket at
http://help.kobobooks.com or email
help@kobobooks.com or call them at 1-866-204-4714 to see if they can sort it out for you. Have your receipt number available as you do this.