Why can't I print double-sided all of a sudden to an HP LaserJet Pro 400? This was working fine until today. Now there's no option at all, and nothing in the "Properties" box.

I'm paying $14.99 per month to use Acrobat Pro DC on 2 computers. I don't have this difficulty on the other one. Why is this now a problem? I just "upgraded" to Pro DC, and now I can't print double-sided. This is very inconvenient.