CAR LOCK FOB on 2004 Chevrolet Malibu Maxx

My car lock fob has stopped working. What's the problem and what will be the cost.

Asked by for the 2004 Chevrolet Malibu Maxx
A semi-circle of metal, that encapsulates the flat battery breaks loose from two areas that have been soldered - get someone to resolder and it should work okay assuming the batteries are ok.