Basic Controller Install Question - Brivis Networker v3

[phibes4000]

I just bought one of these and think I may have a dud.  I connected the TW1 & TW2 wires to my Brivis Buffalo heater, and the screen was blank - I can't get the controller to power on, but the burner starts with it connected. I'm getting voltage on both wires and when I put my old thermostat back on it works fine.

The controller has 2 sets of terminals ala:

A...

TW1

TW2

B...

TW1

TW2

I've connected the 2 wires (grey, grey/white) to (A) TW2 and TW1, and tried reversing these with same effect?  Any ideas? An installers manual would be great!

Lee