You're not getting any more tasks because that's the end of the game. You can keep playing after the credits roll for the sake of things like going back and getting trophies and doing side content.
Iris you either have to get before the end of Archibald's segment, or you have to give up enough to make Archibald not hate you (which is what that Writ is for from the beginning of the game - it serves no other purpose) so you can still get into the mansion. You can make that easier on yourself over the course of the game by doing things that improve your reputation, the most repeatable of which is doing things at Big Dick's Estate.