I too am experiencing this problem, I just did 8 consecutive missions where after completing the second round it would say that both rounds 2 & 4 rewards were "NOT ELIGIBLE DUE TO INACTIVITY" even though I only completed 2 rounds. I have tried Mercury (Odin), Venus (Cytherean), Earth (Gaia), Mars (Alator) & Ceres (Cinxia) plus I have tried all 4 party types (Public, Invite Only, Friends Only, and Solo) as well. Please fix this soon, I am trying to farm for Natural Talent and this is the only way to farm for it so until it's fixed I may as well have no way to obtaining it except by some miracle one of the Grustrag Three drop it when they decide to spawn during a mission which is a very rare chance of happening.