2011 enclave quit blowing air out of dash vents but blows everywhere else in car

Welcome to the forums!
Chances are if the air is blowing at all other locations correctly, but not through the dash vents, it will more than likely be one of the electronically controlled actuators.
There are a few under the dash.
Possibly someone has the schematic & can pinpoint which one exactly needs replacement.

Workaround not fix: Try turning the blower totally off. Then turn it on starting with the blower on low. See if it will direct air out of the front vents. Sometimes when the actuators get tired they'll still work without much air pressure against them. Beats taking the whole thing apart, or at least buys you time before you have to anyways. Again long-shot workaround, no guarantees.

You would have to find the mode actuator under the dash and command different positions and see if the indicator on the actuator moves......if it doesn't, it can be removed, and you can manually move the linkage to see if the door is free....if it is, then the problem is the actuator, wiring or control head....most likely it'* the actuator...the gears are known to strip......you can also apply power and ground to the terminals(white and tan wires), to see if the actuator moves...if they don't try reversing the connections....if it doesn't move, bad actuator...if it does moves, either wiring or control head.....