I've just had the same problem, neither remote actives the central locking, use the key in the drivers door and the locks pop open and closed all round but the alarm triggers when you open a door and only shuts up if you dock the remote in the ignition lock. Car starts fine so the sensors in the ignition system are fine.
Initially I thought driving through a flood had done it, but I realised I had the tailgate open in the rain ( very heavy rain too). With it up. water runs into the valley left by the inverted tailgate and the spoiler and gets under the join. Guess where those cunning Germans hid a very expensive and moisture sensitive piece of electronics. The RF signal from the remotes is not being picked up and passed to the alarm system.
My local indy specialist is replacing my diversity module when it arrives at a cost of £168+vat just for the part as it was drowned and by the look of it for the second time too.
Appalling design IMHO if you can't open your tailgate in the wet. I shall be investing in some silicone sealant to waterproof the new module and seal the gap between the spoiler and the glass once it's back.