Image doesn't appear unless I hit the Set Native Size button

I'm programattically creating an image using a sprite:

 MyImage.sprite = Resources.Load<Sprite>(spritePath);
 MyImage.SetNativeSize();

but the sprite doesn't show up unless I hit the Set Native Size button in the inspector. As you can see, I'm already calling SetNativeSize(), and hitting the button doesn't actually change any values in the inspector (the size is already correct before I hit the button), in both debug and normal view.

I've also noticed that changing the size in the inspector (e.g. adding one pixel to the width) also makes the image appear.

What can I do to make this image appear without necessitating an action in the inspector?

Thank you.