My mechanic says they’re unable to pursue this problem my 2003 Land Rover discovery II is having with the key fob.

Key fob unlock and lock worked when I got it a few weeks ago, but stopped at some point.

now It doesn’t, mechanic says it’s a “mislock” issue? That it thinks a door is open, so it won’t trigger the lock?

anyone have ideas about this?

 

Does the horn honk when you try to lock it? That's the response it should have if you try to lock it and a door or the hood is open.

 

nope, nothing happens - and the horn does work

 

If it's a mislock, on a North America/US spec D2, you will get the horn honk indicating a mislock. All 5 doors and hood.

Also, the RF receiver in the headliner does actually go bad on D2's. (I have a spare since I've suspected it once or twice)

Some questions:
If you insert the key in drivers door and lock / unlock -- do all 5 doors lock / unlock? (if not the one that is not may be a door latch issue).
Do you have 1, or multiple key fobs? It could literally just be a bad key fob. (you say "the key fob" so I ask)

Even though it's not official troubleshooting technique, for example, when the drivers door latch on my D2 failed, I was getting all sorts of odd security system issues, most notably the alarm going off all the time randomly, and the drivers door not locking but always unlocking. Once I replaced it, all was normal. So these issues can be insanely frustrating.

You may need a Land Rover specific mechanic (guessing you are using someone who doesn't just focus on Rovers?). This is fixable.