Assuming the hardware is physically intact, Windows may have corrupted the driver or put the USB port to sleep.
Before diving into advanced fixes, identify which version of the N520 you own. n520 keyboard not working
If you have completed all seven steps and the keyboard remains unresponsive, accept that the hardware has failed. Fortunately, due to the N520’s low cost, a replacement is readily available at most electronics retailers or online. Assuming the hardware is physically intact, Windows may