Just wanted to share this information in case anyone else runs into it, I did a quick search and nothing.
Subject Car: 2007 B7 Audi S4
Problem: No air flow through the Dash, Vent, or Foot wells on ECON/Auto/AC, even with selective vent.
**If you enable air re-circulation, everything works as expected**
Troubleshooting/Diagnoses by Tony over at Pure MS, determined a defective climate control unit.
Resolution: Replace climate control unit
Hope this helps...