java finch help needed

[handyman]

i have 2 pairs of javas, white and fawn. i am using cage of these sizes w18" x h24" x d24". first when i bring javas i put a budgie size clay pitcher in cage which they started nesting and use coconut fiber and papers to build their nest then they throw them back on cage floor. i talk with other bird keeper the said put a nest box of java. i buy 2 nest boxes from pet shop and hang them out side on front of the cage. now after a week i checked the box they did't started nestin i observe them whole day they did't go in nest