I'm having this problem with 3 month old chickens I've showed them where to go and where to roost for 3 weeks now and still no light bulb going off for them :-/ once inside they run back out into yard weather dark or not their brooder was in there as chicks I've offered treats keep food and water in there they go in to eat but they just prefer the yard hoping when the hens start laying they figure out what the nesting boxes are for cause I don't want to have a easter egg hunt every day lol