There is no standard defining the polarity of the JST plug of a Li-Po. Therefore, manufacturers of Li-Po's and manufacturers of battery powered products can determine the polarity themselves. As a result, it regularly happens that the polarity does not match. To avoid damage, it is important to always check the polarity before connecting a Li-Po.
Fortunately, this is fairly easy to solve by removing the wires from the JST plug and connecting them the other way around. Use a thin object such as tweezers to lift up the plastic tabs of the JST connector. Then carefully pull the wires out of the plug. Now put the wires back in the plug the other way around.
