Door Not locking
 

I noticed today that the front passenger door on my CX9 2011 does not lock at all. I don't know since how long the issue is there but I cannot lock it with the smart key, the door button or even locking it manually from inside. It sill can be opened from outside without the key.

I noticed as well that the door-lock knob does not move when I lock or unlock. it is always stuck on lock position.

What do you think is the issue and is it an easy fix?

Easy fix? technically yes.. but it still requires pulling off the molding and investigating the linkage between the locking control bar and the doors latch mechanism. If you can't manually lock it then there is an issue around that point.

I am having this very same issue, have you found a fix??

There is a rod that connects the inside mechanism to the side rotating piece that locks the door. There are plastic clips that the rod moves through. If the clip is broken or the rod is outside the clips, then it can not engage the lock.
You will need to pull the door panel to find out. A reputable shop can probably correct this for no more than an hours labor.

Thanks gmaddox, that was exactly my problem, the rod was out of the clips. I was able to do it myself, took me about 10 minutes!!