If you could not charge or turn on the helmet as usual, please take the following steps to fix the problems. During the charging, please plug in and pull out USB line (charging line) from the USB interface (port) on the helmet for several times. After the practices of plug-in and pulling out, you press on the power on/off button for at least 3 seconds and then you will hear the power on voice message. The plug-in and pulling-out practices serve to reset the power-on function.Please note that the practices should be made in charging state.