Show screen capture as UI image

Hello, I'm trying to take a picture of the screen and assign it as a sprite for an UI image.

However, for some reason, all I get is a white sprite.

 public Camera renderCam;
 int photoWidth = 100, photoHeight = 100;
 
 public void LateUpdate()
     {
         if (snapped)
         {
             RenderTexture rt = new RenderTexture(photoWidth, photoHeight, 24);
             renderCam.targetTexture = rt;
             RenderTexture.active = rt;
             renderCam.Render();
             Texture2D screenShot = new Texture2D(photoWidth, photoHeight, TextureFormat.RGB24, false);
             screenShot.ReadPixels(new Rect(0, 0, photoWidth, photoHeight), 0, 0);
             renderCam.targetTexture = null;

             GameObject flyToHud = GameObject.Instantiate(photoToHudAnimation);    
             flyToHud.GetComponent<Image>().sprite = Sprite.Create(screenShot, new Rect(0, 0, photoWidth, photoHeight), new Vector2(0, 0));
 
             Camera.main.targetTexture = null;
             RenderTexture.active = null; // JC: added to avoid errors
             Destroy(rt);
             snapped = false;
         }
     }

I'm pretty sure the problem is with Sprite.Create(), for 2 reasons:

1) I tried saving the RenderTexture rt to disk as PNG right before the Sprite.Create() method and it worked, so it is indeed storing a capture of the screen.

2) I also already tried simply assigning a public sprite otherSprite to the instantiated object like this:

 flyToHud.GetComponent<Image>().sprite = otherSprite;

and the proper sprite was shown. So I'm sure there is no other part of the code replacing the sprite with a white rectangle.