I'm looking for the name of a short story about a man who has a pact with the devil that requires him to to get a story about a pact with the devil published in a magazine. The editor keeps turning him down. It shows the editor himself has a pact with the devil not to publish short stories about pacts with the devil.
If At First You Don't Succeed, To Hell with It by Charles E. Fritch. First published in the August 1972 issue of The Magazine of Fantasy & Science Fiction. That issue is available to read online at the Internet Archive here.
You may have read it reprinted in an Asimov edited collection, "100 Great Science Fiction Short Short Stories".
The story is only a few pages long, but very funny. It is written as a series of letters between the author and the magazine editor. The author tries repeatedly to sneak variations of the story past the editor with titles like Pact with a Devil's Food Bakery and Packed with the Devil Fish.