Byron SX - Door chime debug

Hi,

I have 2 x "Byron SX 4" door chimes and 2 x wireless buttons.
The back door button I can learn as an "Input Device" from the HS3 plugin. Works fine! :)
The front door will not learn at all! Even if I am right next to it! It is a slightly different model to the backdoor button.

So.... I thought I would try some debugging.
Fired up RFXmngr to see what is going on...
So I first test with the known working back door button... Nothing on the messages panel!?
I can see LighwaveRF and Oregon Scientific sensors flying past, but no Byron messages!
If I select "ONLY" the Byron SX protocol, still nothing :(

Any ideas?

Cheers