Oh I know what's happened. So the last hotfix changed a bunch of things with the notable mechanic, including dropping the amount of gold they carry from ~30k to ~10k. The price of the player selling a workshop in a town with 4177 prosperity would end up being roughly 11500 gold, and since notables don't carry that much gold anymore they can't afford to buy it from the player. Just a small oversight.
@mexxico This is something you might want to look at. Just boosting the max gold threshold back up to 15k or so would probably work.