My nikon d3100 camera playback mode is not working?

My nikon camera works fine but all of a sudden if i click on the playback folder it says the option is not available and also my live view does not work, its just black, please help?

Why do you think you need live view? Unless you are shooting video, you need to be using the cameras viewfinder so that your camera is stable due to your holding the camera against your face, holding the camera with both hands (see page 25)

If you need to confirm that your exposures are good, then you can use the Disp button to view the images on the memory card, but typically as you learn to trust the lightmeter on the camera you will not need to continuously looking at the LCD, "just ot make sure" Using the LCD on a continuing basis will deplete the battery, giving you fewer shots on a full battery.

I suggest you spend some quality time with your camera in one hand and the user manual in the other and learn what controls there are on your camera and how to use them well.