My eldest daughter didn't crawl until 13 months, I remember moving her toy out of reach to try to encourage her to move, nah, didn't bother her, she just sat and scratched at the flowers on her plastic playmat, she finally walked at about 15/16 months old.
My son's youngest didn't even support his own weight with help until it was picked up at nursery when he went at 13 months, finally crawled a couple of months ago and now began walking about three weeks ago. Obviously they do it when their ready. Nothing wrong with either of them, my daughter is a bio medical scientist, and is a pretty laid back person!!