Going to be hard to explain without having you read a tutorial, so I’ll send you to that one first:
What happens is the lid camera is looking for a specific height relative to the top of the tray, when it’s focusing the camera for placement. Be sure the height that you are entering for your unknown height is the difference between the height of the material and the normal top of the tray. (And you might need to lift the object on some scrap wood to get it into the correct range.)