If the charging brick and cables are working, make sure there is no debris on the charging area or the back of the watch. Remove any stickers, including the serial number sticker, if present. If it still doesn't charge properly, send it in for warranty repair. Typically, a failure to charge is due to an improper connection, preventing the watch from receiving enough wattage. This causes the watch to overheat and fail to charge because it is powered on and drawing more power than it's receiving. One other thing you can try before sending it in for warranty repair is doing a manufacturer reset, wiping the back of the watch and charger off, and seeing if it charges. But regardless, you have a year warranty, so though it's understandably frustrating, it might be your route.
