Endless possibilities from improper mounting without sponge gasket and small crack in bezel resulting in water damage, to pressure washing into the chart slot; just not worth speculating. I would recommend removing the chart card, and all cables (except power) then attempt to power up the unit and see what happens. If you are providing good power directly to the back of the unit (Check because corrosion in a power cable can cause loss of voltage/amps) it should provide a double beep and boot up. If it still shows nothing on the screen (not even a color bar at the bottom) then the boot loader software is blown (maybe by someone attempting to upgrade) or you have a serious issue with the display that needs evaluated by a dealer or the service center. Although we stopped selling the 7" NavNet displays awhile back, there are still parts and support for this unit. Since it is a smaller unit to mail; I would recommend the factory service center. They are really good and I have never seen anyone walk away unhappy.