The machine needs maintenance.

Once this message appears, it is recommended to take your machine to your nearest authorized Brother dealer for a regular maintenance check. Although this message will disappear and the machine will continue to function once you touch "OK" , the message will display several more times until the appropriate maintenance is performed.
 

Please take the time to arrange for the maintenance that your machine requires once this message appears. Such steps will help to ensure you receive continued, uninterrupted hours of machine operation for the future.