I think I got it because I completed most of the quest that was handed out by him. Just assuming there but now every time I talk to him , he has like 6 bounties to offer every week and there's a bounty he has which is the 6th one that ask you to complete the other 5 bounties for him. Once you do that , you turn in the bounty that requires you to finish 5 bounties and you get nightfall tier rewards. I got like 3 eyasluna a nlb 310 and several legendaries already.