Cant click with Flash on

Your problem may be due to corrosion on the contacts inside the camera which can prevent the full power of the batteries from flowing into the camera. Remove the batteries and wipe the camera contacts firmly with a dry cloth (heavy corrosion may require cleaning with a wire brush, steel wool, or sandpaper). Remove any residue that may have fallen into the battery compartment during cleaning, then wipe both ends of the batteries and place them back in the camera. This cleaning clears the problem about 90% of the time. If it doesn't work for you, chances are that your batteries are just too worn to handle the task anymore.