Materials list not listing deck planks

[DeckQuestions]

I'm trying to get a materials list going for decks, but the deck plank materials aren't being factored into Calculate Materials in Area/Room.

 

It does work when I Calculate Materials for All Floors or select the planks individually and use Calculate Materials from Selection. I also recently discovered that it works if I calculate in area from a floor above where the planks are, even when nothing is visible on that floor of the plan.

 

How can I remedy this?