1) Check whether charging dock and power adapter operate normally, and the adapter is connected to the dock properly.
2) Check whether electrode in equipment is in good contact with that on charging dock, and clean the electrode if necessary and try again.
3) If the equipment is not at recharging dock, start it by long pressing power button and then try again.
4) The equipment may be in lower battery level, recharge it for 5-10 minutes and then try again.