Samsung Nx300 Doesn't find flash

I have a Samsung nx300, and I'm super happy with it, except the camera suddenly no longer recognizes any flash mounted on it. I have looked around, and many people seem to have the same problem with their nx300s.

I've tried firmware update, factory reset (which I can't find any information anywhere on how to do), taking out the battery and memory card, and I've tried with lots of different flashes. Nothing works, there is simply no way to take pictures with flash.

Anyone have had the same problem, and fixed it? Please let me know! (I bought the camera second-hand, so I probably won't get a free repair, the original receipt is probably lost (still a month left on the 24-month warranty).

Thanks guys!

Andy