Rattling sound inside my Go Pro, is there a way to fix this?

I have had my Go Pro for about 2 years now, I last used it in August and took photo/videos off it from a holiday. Since then it has not been used but when I tried to switch it on, it won't.

I have tried various solution problems but none seem to work. I can hear within the Go Pro a small rattling sound like something has came loose. I have phoned Go Pro support and explained the problem and their solution is, to give me 20% off a new camera.

This is not an option for me when this could be a simple repair and I am not willing to pay £350 for a new camera, for me to send my current camera to them, and to perform a quick refurb and then sell my camera.

Any help would be very much appreciated.