What does Gertrude Stein mean when she labels something as "inaccroachable" as Hemingway quotes her in A Moveable Feast?

In Chapter 2 of Hemingway's A Moveable Feast,
he recounts Gertrude Stein's telling him that one of his stories was
inaccrochable and then using a simile:  "That means it
is like a picture that a painter paints and then he cannot hang it when he has a show
and nobody will buy it because they cannot hang it either." (p.25, Restored
Edition)

Now, what is the meaning of the simile?  Whether
or not the work is good, no one wants to see it.  Ms. Stein actually told Hemingway that
she thought the story, "Up in Michigan," was a good one.  However, it was not something
she enjoyed reading and believed that others would not want to read
it.