So we have noticed over time the solder joints on the USB charger are getting loose or disconnected. So a fix we found is to add flux to the solder joints then re heat the joints and in some cases we had to add new LEADED solder to make the connection work again. Its as if the power and ground pins are not connecting to the pads on the boards. Try this and if it works then like it and share it its seems to be a issue on all the Kindle Fire Tablets.