I assume you have tryed to find a copy of the applicattion.... The NT631C is very robust, I have had several running for a long time. A blank screen can happen if both back light bulbs have burned out. If the unit was set up to always be back lite...... Connect your com cable to the "other" port that is free, (the PLC ic connected to one of the comm ports) Work through the software until you have selected upload the application, and you are at the "OK" button, don't hit it yet... As posted by Jay in the maual above, the "secret" method of getting the unit into Maint mode is to hit any 2 non programed corners at the same time. Once in maint mode it will look like this (if you could see it): The center of the Transmit Mode button is 4-3/8" down from the very outside edge of the NT631C Push in this area The screen will now look like this: The center of the Tool transmit button is 4-1/4" down. Push in this area. Now push the OK button on you PC, the application should upload. When the upload is done, the screen will look like this: Push the "Quit" button in the upper right hand corner, the screen will resume communication with the PLC. Hope this helps.