Is the battery in the vehicle in good shape? Also when did the keyless entry stop working? Was there a a trip to the mechanic at some point, or did it always not work?
Just trying to do some deduction and see what may have happened.
Customer............another expert here
If you are sure the Transmitter is transmitting a signal, you can try to rysync the Transmitter with the Reciever byStand next to vehiclePress & Hold Lock & Unlock Buttons together for apprx 5 seconds.
If the above does not work, the system needs to be checked for problems, via Dealer Scan Tool.Be sure you have all Remotes at that time
Sorry for the bad news, but that system is not Customer friendly / repaired without the use of Dealer Scan Tool