I'm an old Canon nerd and these controls are familiar to me. I unboxed a used 6DMk2 and I'm unable to fire an exposure in Live View. The Quick Control symbol shows, all settings are normal and this happens in all modes. I can go to Live View with the tilting screen, focus, change settings etc but I can't fire off a shot. My 70D always worked. I can't figure this one out but I'm assuming it's a camera setting (fingers crossed) and not a glitch. Any wise words? What's going on here?