Thanks for the good discussion, everyone!
If you save the building you’re trying to build as a template, and then plop it down in a fresh world with all the required supplies (cheat if necessary), does it build? If it does not build, and everyone is standing around staring, it’s possible that the hearthlings cannot figure out HOW to build it. In this case, head over to this thread and post your template: [A14/A15] The buildings my hearthling will not build Thread
If they can build the building in a fresh world, but not in THIS one, then it may be a memory/gamestate/performance problem. In that case, make a new bug and upload your save.
Thanks!