Is there any way to know why workers will just stop working on a building or any plan to let us know in the future?
I have had it happen with my last two buildings, the latest i made sure it was not touching anything else so that it could be completed but now nobody will work on it and I just don’t know why.
Is there room for the scaffolding. The citizens love using many layers of scaffolding. Also do you have all the supplies?
Try ‘placing’ an item like a rug or lamp to see if that will give them a kick-start.
Last thing: is your game the latest version?
Save the building template and then open up a new world and try to build the same one there to see if it’s potentialy related to your save and not the building itself