Ambient Light not working with some objects

I’m creating a 2D game, and I wanted ambient light for it, so I added on the sprite diffuse shader. It works just fine with most objects, just not a specific one in the scene. It seems to work when zoomed in on it but otherwise no.

Here’s a picture of it zoomed out.

Here’s a picture of it zoomed in.

Do you have any idea why it only works when zoomed in?

I would try this instead if you are using all sprites…