that is because you are too close to the action.
the camera is too “large” and it cuts off when is too close up to an object and this gives the impression of a hole in the image.
you could fix this by changing the Near Clip Plane
Edit → Project Settings → General Settings, there is a Near Clip Plane
but another alternative is to move the camera game object back and then use the lens options to change the zoom. like those 35mm 75mm that stuff
but if is a 2D game better to use an orthographic camera which doesn’t has this near clip issue