If you have the possibility, simply remove the batteries and wait for a while for all the power to deplete. Try turning it on without the batteries. This should consume the remaining power. Insert the batteries back and open it. Under the batteries, there should be a small button. It acts as a reset button. Push it, put the batteries back and then turn it on. If it still doesn't want to work, you might need to send it for replacement or buy a new one because it might be a hardware related error.