I have an 09 Laguna. For some reason the front passenger door will not unlock when the rest do using the fob. Any ideas please ?

Remove the door card and check the connection to the door relay, with luck it's a poor connection. it could also be a failed relay. Check the wiring first, it's cheaper than a relay. It's also possible that the connecting cable which activates the lock could have come off or detached.

its the lock actuator ..when you press the fob it makes the actuator go forward /back ..its a common problem

Could be an electrical problem. or could be a mechanical problem. Either way you will have to take the inside door panel off. This may not be easy to replace afterwards.

Replace the lock actuator.

You might need to replace the door lock mechanism, or it could be a loose wire. If the car has power windows, does the window on that door work? Another possibility: maybe you just have to press the button again. On my car, if you press it once, only the driver's door unlocks. Press again and all the doors unlock.