There are a few things to try, but, generally, restoring operation after an error of this type requires a reprogramming by a Nikon service.
Try a hard reset:
Remove the battery, memory card (if installed) and disconnect any usb cables. Switch the camera on . Allow the camera to sit idle for 30 minutes. Switch the camera off. Reinstall the battery without the memory card and try to power on. If there is no response, plug in the USB cable and connect the camera to the computer and note any activity.
Please let me know the result.
Please keep in mind that my diagnosis & solutions provided are directly dependent on the accuracy of your description of the problem. As with any "do it yourself" fixes, success is a "team effort", since I can't see or touch the camera, and relies on the customer's manual dexterity and ability to follow the instructions well. If the "do it yourself" approach doesn't work out for you and you need conventional repair, please let me know.
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