no air flow from main vents- 2004 Accord EX

[lynnmccraw]

I just bought a used 2004 Honda accord with dual climate control, and the heat and AC work great, but I cannot get anything to blow out of the main front air vents. Air comes from the side vents, floor vents, and defrost vents just fine, and the flow is good. I assume that the dealership I bought it from had already checked for a disconnected hose under the dash because I found one of the panels in the trunk after I got it home. So, if it's not a hose that has come disconnected, what else can it be?? Is this a common problem?

BTW- I have tried every setting: AC off, Auto, Hi, Low, defrost, and every combination possible!