Why my Nikon d3100 won't turn on

I recently purchased a Nikon d3100, and it was working perfect but something went wrong yesterday! It won't start. I tried charging the battery and everything but it just won't start! The battery is working perfectly fine, i tried it on my friend's Nikon d3100 and it worked! I tried putting her battery into my camera. It didn't turn on!

On the D3100, I believe there's a reset button under the panel on the side of the camera, just below the usb port.

Where the button is located.
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Try resetting the camera, if that does not work, then bring it back to the seller along with all the documents you got with it. Bring back even the package (box etc) and explain to them what is happening.