My middle vents are not blowing at all

You need vacuum to change the position of the HVAC doors. On older cars, the vacuum hoses that power the vent doors crack and leak. Check your hoses and replace if necessary.

I have a '05 Lexus gs430 for those who's car similar is having problem with the middle vent no air coming out. I took my car to different mechanics including the dealership and they could not tell what's wrong. Here's what I did. I remove the the center vent it's pretty easy just pry it open and disconnect the the electrical plug. Stick your hand inside the whole and you can feel the air vent is block no air passage whatsoever. Push down to the piece blocking it and you feel it open do the same for the other hole. that's all it took for mine.