Generative Fill says "The Parameters for "Generative Fill" are not currently valid"

I am trying to use generative fill to expand an image. I am in the crop tool and dragged out to the side of the image I want it to expand, but when I click "Generative Fill" I get an error message reading "The Parameters for "Generative Fill" are not currently valid". Does anybody kno what the parameters are or why it may not be working?