I received my sigma 150-500mm F/5-6.3 zoom lens. I connected my lens to my Nikon D3300 which is compatible. When I take a picture the picture is black. I think it's because the shutter is closed. I can't seem to get it to open up. It also reads that the lens is not attached.
If the camera cannot communicate with the lens, it cannot tell the lens to open the aperture to let the right amount of light in, and it probably will meter based on the assumption that the aperture is much wider than it actually is because it can't read the current aperture position from the lens.
Bottom line: Try cleaning the contacts. If that doesn't work, contact the lens manufacturer or the seller, because the lens's electronics are DOA.