I fear I may not adequately describe my issue, but I am going to give it a shot. I purchased a D500 used with a very low shutter count. When I shooting in manual, and I change my ISO, nothing changes with the image. I do not have auto ISO set at all. Is it possible I need to send it to Nikon to have it given the once over? I am really quite unhappy with it. Firmware was updated when I got it in Feb of this year. thank you in advance for any advice.