Why is ReadPixels on my RenderTexture creating a pure gray texture?

Hello, I am trying to create a RenderTexture of the image below to eventually create a Texture2D that can be used in an sprite atlas later. I have found various tutorials and have come up with the following code:

private Texture2D CreateAtlasTexture(int textureSize)
		RenderTexture renderTexture = new RenderTexture(textureSize, textureSize, 24);
		Texture2D atlasTexture = new Texture2D(textureSize, textureSize, TextureFormat.ARGB32, false);
		RenderCamera.aspect = 1.0f;
		RenderCamera.targetTexture = renderTexture;
		RenderTexture.active = renderTexture;
		atlasTexture.ReadPixels(new Rect(0.0f, 0.0f, textureSize, textureSize), 0, 0);
		RenderTexture.active = null;
		RenderCamera.targetTexture = null;
		return atlasTexture;

However, when I run this code, and the camera preview looks like the screenshot below, I get a Texture2D that is 100% gray. Can someone help identify why this might be happening?

I’m missing a atlasTexture.Apply().