"In Honor of Our Fathers" – "The Hunter's Hunt" [Campaign 3, Mission 5]

Alas and alack...((((
I left him a town and heroes, but he still can't manage...

Damn, I've already forgotten, but there should be some kind of clue (condition) related to heroes, artifacts, or troops. Most likely, try deleting and replaying the mission. But closer to the end, don't kill all the secondary heroes and don't capture all the castles, and pay attention to the conditions for completing all the buildings.