Villagers aren't switching professions when there is a valid job site block. It is unclaimed but the villagers aren't attempting to pathfind to it. I have tried this at the times that villagers are supposed to switch professions but they never switch their profession. The villager in the screenshot was a farmer pre 1.16 but he quit being a farmer when the update happened. I am also playing on realms so that might have something to do with it.