Renault plip keys are temperamental.
If the car wont start because of the key its usually because it needs re-programming or its knackered. Its very rare batteries solve the problem and in some cases a battery change can make it worse ( may lose the code in battery swap ) I take it you have tried to re-synch the key & checked the receiver but with no success ? Have you got a spare key you could try ?
Another common fault is the micro switch on the circuit board coming lose and rattling around inside the casing. This is the button that activates the central locking.
These are easy to re-solder and can sometimes cure the fault. I take it the car is starting ? This means the immobiliser chip is communicating with the de-coder ring on the ignition barrel and disarming the system. If the central locking isn't working its more likely that the plip key needs recoding - this is a simple process and can be done via a CLIP diagnostic machine ( you will need your immobiliser code - can be obtained by PM'ing me ) If you have 2 keys make sure they are re-programmed at the same time. If the key doesnt take a code and you have it diagnosed as faulty a new key is £91.76 + vat ( part number 8200067907 or 8200100173 - both same part ) this comes in virgin form and will need coding in ( at extra cost )
If this doesnt work it will more than likely be the multitimer unit / UCH / BIC board thats at fault - these are responsible for most internal electrical gremilins on most Renault's. This is situated above the bonnet release handle on the N/S of the dashboard. New ones cost £168.19 + vat ( part number varies due to numerous supersessions ) 8200065817, 8200621763, 8200387291,
8200234046, 8200311990, 8200272302, 8200207135 - all the same part.
If all else fails or you want a cheap alternative you can fit a second hand ECU kit. You will need to find a donor car with the exact same ECU Part number as yours. You will need the UCH and the plip key as well + the chassis number off the donor car in order to obtain the immobiliser code to program or order another key if required.
A good tip is keep your key away from electrical appliances that emit a high frequency radio wave or infa red signals as these interfere with the plip keys electrics ( mobile phones !! )
