BMW Repair: no air from front vents, center vents, stage unit

Question
97 328i 172K
No air (hot or cold) from direct facing vents on driver/passenger/center vents.  Air comes from top and bottom vents and defrost.  Blower seems to be working.  ? final stage unit/relay or something else?  Thanks

Answer
Not certain, but I believe there's a unit that controls the air going to either the defrost or center, whereas the bottom is it's own.

If you tell it to go to the vents and not defrost, does it go to defrost?

Does it work the same whether set for fresh air or recirculate?