Chosen Solution
My D5200 seems to be working just fine other than the fact that it is not showing an picture on the LCD screen. The screen stays grey when turned on but will not show anything (regardless of if I mess with the buttons). I can still take photos and retrieve them from the SD card.
sounds like you need a new LCD, follow this guide to fitting a new one Nikon D5200 Screen Replacement
I had the same problem sent it away to Nikon who couldn’t fault itso, remove the four lcd retaining screws so you can get in and behind the screen there you will find a small electrical connector ( silver in colour and slides onto the circuit board and clips into place)and a larger connectorI found that the larger connector purely by chance wasn’t located and clipped securely in placeyou’ll see what I mean once it’s opened up… resecured and everything worked as it should reattached lcd screen ,,,never had an issue since
