Passenger front door (not sensing when ajar and cannot unlock)

[chrmbly]

So... Installed an aftermarket stereo probably 4 months ago in my 2014 GMC Sierra SLT Crew Cab...  Only noticed recently that the interior lights do not come on when the passenger door is open.  I have googled this to death and could not find where the sensor is that detects whether the door is open or not (and I looked all over the door and frame for a nub or something).  Where is the sensor that detects whether the door is ajar or shut?

 

Then all of a sudden a couple days ago the same door will not open with the keyfob or with the lock button on the driver side.  Unlocks if I open the door and locks when you push down on the stalk on the door.

 

I think the first problem could be that i buggered something when i was installing the stereo - the door lock/unlock seems unrelated since it happened months later, but hell it could be my fault too.  Any thoughts would be appreciated.  

 

Thinking it's worth tearing apart before i take it somewhere just in case it is something obvious...

 

CB