Air driver side and pessenger side is different

[mikeson]

Hi guys,

Yes, I did search.
Anyway, both passenger side and driver side temp set 60 and turned on air-condition.
It blew cold air and no problem but driver side air is a lot weaker than passenger side.
even both side set same, driver feels like 1 and passenger side like 2.

So I pull out center air vent and find out cover on driver side was closed. (cover that located deep inside), so I manually pushed opened the cover(kind of flip cover that close and open) and then both side air is same.

Does anybody know why driver side flip cover is closed?
DO I have to change something?

Thank you for any advice.
By the way, my car is 2007 X5 3.0