you give zero information on the problem to help with suggested fixes - the purpose of this site is for others to offer repair suggestions. Are you SURE the battery is working? 18650 cells have cutoff voltages - no idea of this cameras setting but below that threshold battery will not charge - and/or the unit will not power on if the voltage is below that threshold - first check make sure battery is close to 3.7 to 4.2v. Next is to ensure the wires in the plugs haven't come undone. Also check for cold solder joints. Cameras on bikes experience lots of bumps and vibrations which can cause electrical disconnections. Ensure the power button is functioning properly (ala with a continuity tester to ensure on/off functioning) - many electronic devices have a 'soft power' and may have additional functions if held. Look for obvious burn/blue smoke damage indicating a failed component. Next components that commonly fail are capacitors - but you'll need a micro farad tester to confirm. Beyond the obvious physical or electrical issues the next step is trying to troubleshoot the electronics...any one component failure could stop everything else.