1 car vent not working

I have a 1996 Toyota Celica in great condition. My problem is years ago the driver side side vent stopped working; in fact, I don’t think it ever worked & I bought it brand new but didn’t notice at the time. Well, we live in the south & it is very hot with no airco coming out the vent. I also get no heat. The other vents work great. I have it opened-I even took the vent cover off, but can’t find anything in there that would help. I also have a small vent under the steering wheel column, it doesn’t do anything either. Any suggestions?

I suspect a blend door is stuck/disconnected or a selection control isn’t working.

The blend door is what directs the air flow. It is located in the ductwork. If you can locate a ductwork drawing you will see it.