Budgies nest box (breeding)

hi,
i own 5 budgies, they were handed down to me from my friends friends. i bought them a new cage and everything. one day i noticed that the 2 females had brown cere(they r over 1 years) so is the male. i put in a budgie box like two weeks ago but they still haven't gone in. when will they go in? when will they lay eggs? they sit on top of it, peck on the hole, peck around it, and just sit by it. but they never go in. when wil they go in???