Fellows,
The chrome door lock pin or knob on passenger rear door sill won’t go down!
When I’m locking the car outside with key, or when I’m pushing down the driver door pin from the inside, all other door pins go down and doors lock, but not the rear right door.
I can’t push it down by hand either.
I tried applying WD40 to the latch assembly, but it doesn’t help.
It’s not a good situation as I am street parking, and that door is now unlocked.
Thank you for any advice!
1995 XJR
Take the door card off and se what’s stopping the lock button from moving.
Interesting question, in that I have just the opposite situation with Harlem’s left rear door. You can hear the lock relay activate in it when the key is turned (on the driver’s door), but the door will still not unlock. You can see the knob move a little, but not much. It’s like something is interfering with the unlocking mechanism. Pulling on the inside handle is of no effect, either and you can’t force the knob up by pulling on it manually. I noticed that, since a friend of mine returned it to me a few years ago, there is a small dent in the door in the area just below the door handle assembly. I can’t recall if the issue started right after she returned the car to me, or later on. Not much, and I wouldn’t think not large enough of an “inward intrusion” to interfere with the mechanical operation of the locking mechanism. 
This is where it gets interesting - how can you remove the door card with the door frozen in the closed position? Is that even possible? 
What’s the status on this one?
I haven’t had a chance yet to open the door panel to see what is blocking the pin. It’s too cold outside to do this. For now I wrapped the seatbelt around the pin to hide its “open position”, as I am street parking the car.
Brought it to the shop and it turned out to be a broken actuator.
Thanks for all your feedback!
btw, by way of update here, friend was finally able to get the door open last month, by working through the door crack on it. 
Not sure still why the lock does not unlock using the key on the driver’s door (don’t have the new fob programmed yet) or when attempting to pull the knob upward. He did note that I was not correct in that the knob does not pop up when the key is used. It apparently does (or at least does now), yet has no effect on the “lock” (latch) itself. We think now the small dent has nothing to do with the problem, mostly likely. 
Glad you got it resolved. 
Mine w. Harlem is still a “mystery” of sorts, as you can read just above. Doesn’t sound like the actuator is at fault in my case, as the knob does pop up (now) and you can hear it make its sound whenever the “unlock” is activated by using the key in the driver’s door.