The clicking noise you hear from your camera is the infra red turning on and off as it moves between standard daytime and night vision modes. It's perfectly normal and isn't anything to be worried about.
It may happen in the early morning and late afternoon when the amount of light is marginal. It may also occur if the camera is in a room with a TV nearby as the changing light from a television in a darker room can significantly influence light levels.
To reduce the clicking noise we recommend not placing the camera near a TV or locations where the environmental light changes frequently.
You can also turn off ‘Automatic Camera IR’ in camera's settings page. This means the camera will no longer automatically turn on it's night vision infrared light.