E36 Remote central locking not working

[Kobra 180]

I've recently picked up an NZ new 1996 (12/95 build) E36 328i.

The car came with 2 keys, both are OEM 3 button ones like below. But one has an LED and takes a single big battery, while the other has no LED and takes 2 small batteries.

They both work fine when used manually, but none of the button functionality works on either. 
I've replaced the batteries, but that has made no difference.
Central locking in general seems to work fine, with all doors locking and unlocking together.

My first thought is that they've lost their pairing with the car. I've attempted several different methods to re-pair them, but the car never seems to respond on the final step after pressing the lock button 3 times (although the led lights up on the key).

I've checked all of the Central locking fuses, and they all look fine.

I'm starting to think there is an issue with the receiver in the rear view mirror.

Any help would be greatly appreciated. 

[Gaz 1062]

Did you manage to sort this? If you are in town come see me at Chch BMW and I'll give your keys ago to pair them

[Kobra 180]

Nope, still not sorted. When would be a good time to come by?

[Gaz 1062]

Anytime really. I'm there 8-5 Monday to Friday 

[BMS 0]

I’ve got exactly the same issue, central locking works fine manually but key fob won’t pair? Did you ever get to the bottom of your fault?

[andreas511 0]

What was the issue?