The battery is supplied loose with the scale - if the battery compartment is unscrewed and the enclosed battery is inserted, the scale may not work.

This is because the contact flags both press on the same pole of the battery instead of one touching the positive pole and the other the negative pole. Using a pointed object, bend one of the flags so that it touches the battery on the underside and the other flag so that it touches the battery on the side. If the battery is then inserted and the battery compartment closed with the four small screws, the scale will fulfil its function.