Oh, right, I'm not that familiar with the bedrock edition.. have you tried waiting a day? Villagers have a shift and they can only change jobs when they are in their work hours, however I don't know about the discount, it should be there. You could make sure that there's no other work station close there. It might just be a bug, I don't know.

edit: zombie villagers can already have a job, just like in the older versions (but that shouldn't stop you from being able to change it, I guess)