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?
It sounds a distinct possibility. Is this happening with both lenses or only one? Can you take the offending lens(es) to a camera shop and try them on a different body? Here is a link where someone was having what appears to be the same problem:http://nikonites.com/d3200/19507-auto-focus-not-working-d3200.html
Which focus mode have you selected in camera settings? The in-camera settings for focus modes also allow you to turn off autofocus without changing the focus button on lens. Check to see if you accidentally set this to manual.