I have a EOS 6d mark ii As soon as I turn it on it turns it's self off, I tried it with two different Canon batteries and memory cards and lenses, still same issue. It was working correctly before the issue started.
I have already tried what Waddizzle suggested but still turns off a few seconds after it is turned on. I had this issuse once before but it corrected its self, but tyhis time. The camera is fairly new but out of warranty, I have only used it a few ...