I find that my drivers door is hard to work after washing the car one check that I do is take the key out and hold it to the middle of the drivers window but sometimes that has no affect. So your left with three things is it the key or is it the handle button or is it the receiver, I have a Renault clip so I must check with it tomorrow as you can tell when buttons on the dash are pressed or not so I think you should be able to see if the door handle button is pressed somewhere. I don't think it is the key or the receiver as the door always unlocks which means the key is seen by the car. If you have a second key I would try that for a while and if the drivers door does not lock try the passenger one to lock it go back to the drivers door put your hand on the handle to unlock it if that works the key's fine stay in the same position and lock it with the handle button again. It's like mobile's is it the phone, sim or network that's crap, my car has been polished and the paint is off the passenger door handle so I might replace both because they look as bad as a kerbed wheel. Make sure the key is not sitting behind your phone inside your pocket and the key pocket is not facing away from the car when you press the button.
