Perhaps the editor has just bought a story similar to the one you have written. It's to do with marketing. As a writer you must do your market research. Read the type of books you love to write and see how yours differs from the published author's. If the type of books you love to read are not on the shelf, then you are going to have a harder time making that sale.
Many frustrated writers decide to self-publish.
It's expensive and few bookstores will take any vanity press novels. But the majority deal only through a distribution network. You have to become your own distributor, your own publicist, etc. You have to be willing and able to self-promote yourself and your book way beyond what is normally expected of an author. If you can't do this sort of thing, you could employ someone to do it for you, or you may end up with hundreds of unsold books and a large printing bill.