Registering My Sins Diplomacy?

If you bought Diplomacy as a stand alone (I.e. not through Trinity), its already registered and you should see the reduced price when you preorder from this website. If you got Trinity, register it on Impulse and go to the Sins store.

Thanks. Yeah, its a stand alone.

I bought Diplomacy not through Trinity. It is registered with Impulse as are the main game and Entrenchment but it just wont appear here in my account -> registrations thus not giving me the discount, any idea how to fix that?

If you are logged onto the forums then you can use the store button to buy it. It will automatically deduct the cost. At least it worked that way with me just now.