Started a new town in Riverview.
Set a 2 story home from the library.
Removed the existing stair, and replaced installed stair with a circular one
Cannot click on the stairs. Can go upstairs by clicking on go here or an item upstairs.
Could not go back downstairs.
Turns out the stairs cannot be against the wall. If one side of stair entry is against the upstairs wall, they can't go downstairs.
New build, 2 story. Made sure the Bottom and top entry was not against the wall. Could go up and down by clicking go here. Still could not click on stairs.