I bought a Nikon D3200 DSLR with 18-55 and 70-200mm lens. I was taking photos for week in autofocus mode, where I have to press shutter button halfway to focus. And then I switched to manual, where I have to turn the focus ring on the lens to focus. But now, when I switched the lens back to autofocus (switched the small button from M to A on the lens) my camera doesn't autofocus any more. Is my focus ring damaged?