So in this example, I draw an actual deck and a sample deck on the 2nd floor plan, as in the tutorial, with straight deck railings under "Build Deck Railings." I check to make sure it is a deck in the room specification, and it is. The structure and height are correct as below. Auto rebuild deck framing is ON. I go to the layer panel and reset all layers to "checked." Default auto rebuild framing doesn't have any effect. The deck and any sample decks build but display as in the tutorial video.
MichaelScott's post in Deck not displaying correctly in 3D view was marked as the answer