Gold and Green Fobs

I fitted a Land Rover approved immobiliser spider kit to my Defender some years ago but for various reasons never got around to programming it. Now that I'm trying to get it all working, I'm unable to get the gold fob to make the sensor bleep to enable the programming of the two green fobs. If I use a test light probe on the ribbon wiring from the spider to the sensor it lights up and the sensor bleeps, so it proves that power is getting through from the spider. I can't understand why the fobs are not doing anything as they have been stored in their original box since I bought them and not dropped or knocked about. Has anyone else had similar issues with the fobs ?