Don’t honestly know what caused it, but telling my Hearthling to promote after a bit of play, and they basically won’t.
The only time I’ve had this happen was when my Hearthling was stuck somewhere and couldn’t physically get to the stockpile with the tool in it (they had found their way on top of a cliff with no ladder). Didn’t notice they were stuck at first, until I went looking for him to find out what he was doing. Just in case that is/was the cause rather than a promotion bug.
That may have been. But at the time of first attempt he was gathering resources, and upon a save / load, everything was fine. Mayne just a random glitch?