Chicken coop information/help?

i have recently bought 3 chickens , 2 sus and a plymouth. in the coop i have a free roaming area at the bottom and the perches and 3 nest boxes are suspended approx 10inches off the bottom. since i have had the chickens they never go on the perches on in the nest boxes! just stay on the bottom, are the perches/boxes to high? surely they can jump that high or climb? i have put a ramp in as well?