“Help! My Stories Aren’t Selling.”
Firstly, how many stories have you written? If you’ve written fewer than 30, keep going.
Next, read. Authors publish their ebooks as freebies. Download them, and read. Here’s Amazon’s Top 100 Free in Paranormal Romance, for example. Read widely.
You’re not reading to copy anyone. You’re reading to improve your writing, overall, by enhancing your command of language and by absorbing story structure. The best novelists and short story writers understand people too, so read the THE 50 BEST SHORT STORIES OF ALL TIME. You’ll find the stories in short story collections in your library. Older stories are available at Project Gutenberg – here’s Chekhov, for example. I regularly reread his: The Lady With the Dog, it’s wonderful.