I have the same problem. One villager was assigned to farming - she didn't get it. Then building - didn't get it. Then research - finally she got it. And before anyone says anything about likes and dislikes, I checked and she had no likes or dislikes related to any of those fields of work My advice would be to keep trying all different types of work until you find something the villager will do. Also sometimes it can take a few tries before they will get it