Drivers rear side door doesn't lock

Check the child lock. If it does not open from earlier side then inner panel needs to go out snd see what's heppend. Not sure how locks designed on it, it could be that power lock actuator lever snapped from it's place

If all of the other locks are unlocking and only the drivers door is a problem then it is likely that you have a problem with the central locking pump on the door lock. This is one unit and the entire door lock will need to be replaced.

central locking not working unless you slam the one particular door very hard [renualt laguna 2000

reset the central locking system by locking car with key in drivers door and hold key over for 30 secs.then pressing and holding down unlock button on keypad OR unlock door with key and hold key over 30secs (windows may go down, thats okay,some cars are fitted with auto windows)then press and hold lock button on keypad.making sure that in both cases you know the keyfob battery is in good nick....should reset system

It's unlikely you can rectify this problem by playing around with the CL system so you will need to take it to the dealer or auto electrician to fix.
In any event you should be able to manually lock all passenger doors on the vehicle from inside the car and the drivers door from outside with the key.

Before you take the car to the auto shop to fix the CL system try this if you have not already.

1. Manually lock - then manually unlock - all doors (except the driver's door) from inside the car and make sure they are fully shut.

2. Then manually lock all doors a 2nd time except the driver's door.

3. Hit the lock button on your car key pad to activate the central locking system. This should lock the drivers door but with the fault it probably won't. Wait a few seconds then hit unlock on your key pad. Wait again and then hit lock once more. If it will not lock all doors you know what to do next.

you may need to replace the drivers door locking mechenism common fault on peugeots

change solenoid in drivers door.

http://www.honestjohn.co.uk/forum/post/?t=69400

If all the doors do not lock or unlock when using the passenger side switch, then the switch itself is probably bad.   If the passenger side switch locks or unlocks all the other doors except for its own, then the power lock solenoid inside the door is bad or jammed.  If it is jammed, try locking and unlocking the door manually while activating the switch to work its way free.

dont blame the idiot,we all make stupid mistakes without thinking and iam no exception,remove door trim and oil the solonoid with a oil can not a silly sunday mechanic spray and let it soak in as its working but i think its just a bit sticky with wear and dirt ingress hence it locks but doesnt unlock which might need a bit more power,oil the whole lot lock and all