It is up to him how long he takes to reply. If you have sent a notification of court with the divorce papers then he is bound to answer it within the stipulated time otherwise you can't force him to reply. He can contest the papers if he is against this divorce.
I Sent My Husband Divorce Papers. How Long Does He Have To Reply, Whether He Contests Them Or Just Signs Them?
He doesn't have to sign anything really. You have to go through a lawyer and set up a court date if he doesn't depending on how soon you want the divorce.