Did a search but couldn't find anything to help.

So here's the story, I was alternating key fobs to keep them charged. Got to work and locked up the car, but when I left the fob wouldn't unlock the car so I used the emergency key. Now the passenger door won't lock. every other door will lock and the mirrors will fold away but I can still open the passenger door making the alarm go off.

Any ideas? I've tried "re-locking" with the emergency key but still nothing. Am I looking at a new locking mechanism?

I'm hoping there's a nifty trick like holding the window switch up for 5 seconds to re-enable the one touch function which I found out from here a couple of days ago (it was really bugging me 😂)

Sounds like you are in for a new locking mechanism. There seems to have been a few posts on this subject recently and when I called the dealer the response was to the effect that it was a common fault. I have exactly this but on the driver's door. The dropping all of the windows function is the best way in although I am always a bit wary that it might blow a fuse -(this happened to a friend once on a different car and the windows stuck half way down and it was raining heavily !). Other route in is via the tailgate  3 x FL1 2 manual + 1 auto
5 x FL2 4 manual + 1 auto
Now Discovery Sport P250 MHEV SE

It's fine getting into the car it's just that the passenger door won't lock, and it conveniently happened just after I used the emergency key for entry. Looks like a trip to a garage at some point then.

Cambelt service is top of the list currently though