This should be quite simple to fix.
From your description of the problem ...
1) You have two key cards that both fail to operate the central locking.
2) Both key cards operate the immobiliser and allow the car to be driven.
3) The central locking can be operated from the switch in the centre console
4) The light in both cards operate when buttons are pressed.
Since both cards exhibit the same fault I would discount a problem with these.
Also, since the cards work the ignition they must be programmed to the car and also be active (There is a function to have cards that are programmed to a car temporarily disabled).
The RF receiver for the key card is located in the card reader. First get in the car, hold one of the key cards close to the slot and try to lock the car.
If this works then move further away until it stops.
This may be caused by external interference as previously mentioned.
If this still fails to lock the problem is with the Card Reader, the wiring, the connectors or the
The easiest unit to replace is the card reader since this simply unclips and is not programmed to the car.
Remove the reader and check its condition and the condition of the connector and wires.
With the reader removed from the dash; looking at the front, the connector is on the right hand side.
Looking at the connector the two signal wires for the central locking are the left most pins on the top and bottom of the connector (pin 6 top and pin 12 bottom)
If the problem is not with the card reader a replacement
may be required and will need specific configuration programming by Renault.
I'd see if you can get a card reader from a breakers first.
Since fitting is easy you might get to test it at the yard.