Plug your unit into the charger and leave it charging for at least 4 hours straight. Use a different wall charger and USB cable if this does not work. If the unit still doesn’t charge, please contact support. DO NOT attempt to disassemble or replace the battery on your own. DO NOT open the unit. It will no longer be waterproof! If your unit is out of warranty, you can find replacement batteries on 3rd party’s websites and in specialty electronics retailers. That said, we DO NOT recommend replacing parts on your own for the risk of water, dirt, and general electronic damage.