Staring up again - sound from Prologue, not from Halion

I’ve returned to computer recording and have just installed a very old version - Cubase 4 - on my Macbook to crack all possible problems before I invest a lot of dough in the latest version. I’m glad I did because I have already come up against a problem with is baffling me. (Back in the OS9 days I did a lot with Cubase 5.1, so I’m not a complete beginner.)

My problem is simple: because of the way I used to work, I tried to set up a midi drum track to get a basic beat down to the tune I want to record. Simple, I thought: create a new instrument track, select Halion One and then get started inputting the beats. Fine, except there is no sound out and nothing is listed in the device setup.

But the odd thing is that if I change the same drum notes to using Prologue, there’s no problem at all - sound comes right up.

I am beating my head against a brick wall here. It is obviously some very simple setting I have overlooked but I can’t for the life me find out which one it is. Can anyone help me?