Image exported does not match image in Photoshop

When I export my document to a sRGB PNG, the image exported doesn't match what's shown in the document in Photoshop. How do I fix this? I've attached a screenshot of the document and the exported PNG image side-by-side, where you can see that the black-to-transparent gradient appears differently in the PNG. In Photoshop, the girl next to the boy is visible, but in the PNG, the girl is not.