Sprite image not showing up when assigned to Texture2D

I have a UI image component that I am trying to give a new sprite at runtime from the following code:

 public Image overlayImage;
 public Texture2D puzzleImage;
 [...]
 Rect overlayRect = new Rect(overlayImage.rectTransform.localPosition.x, overlayImage.rectTransform.localPosition.y, puzzleImage.width, puzzleImage.height);
             overlayImage.sprite = Sprite.Create(puzzleImage, overlayRect , new Vector2(0, 0), 100.0f);
             overlayImage.SetNativeSize();

However it does not show up in game, the image loads in as it correctly assigns the size of the image, any help appreciated.