Humidifiers and Dehumidifiers - Wiring question w/ Aprilaire 400 and Bryant Zone Perfect Plus

So we've got the Aprilaire 400 humidifier installed in the duct, with the water and all. However, we're trying to *not* install Aprilaire's humidify controller because on my furnace already is Brant's "Zone Perfect Plus" controller connected to a thermostat. This controller's instructions says that we should use its humidifier controls instead of any other. Plus, by using it, we can control the humidity from our thermostat.

Anyway, the bottom line is that it's not working. I verified that the thermostat is set to send power to the "HUM" 24 VAC output terminal on the controller when the fan and/or heater comes on. On the equipment controller in the basement, a little light next to the HUM output comes on at this same time so indeed it seems that things are working. However, when I hook a voltmeter across "HUM" and the common "C" I got no output (0V). To check things on the board, if I move the red probe from HUM to something a couple connections away labeled "NC", I get 28 VAC registered on the voltmeter.

So, it would seem the humidifier would work if only it got power. I just can't figure out:

1) Why do I get no voltage at the HUM port no matter what the situation is? Is there simply a defect or is not configured properly? Is there any reason not to do this...I like the idea of having the humidity control in my existing thermostat.

2) Anyone else try using their furnace controller instead of Aprilaire's humidifier's control?

Thanks

I have not delt with this type of control... How old is the control? Maybe it's a defect?

Contact your dealer on this.

The furnace (and house) are only 5 years old.

I had a somewhat handy friend come over and take a look, and he couldn't see that I was missing anything. He suspects that somehow the relay which switches on the power for the humidifier terminal when the controller thinks there needs to be more humidity is broken. How likely is that? In a 5 year old house that never had a humidifier, how would that relay be broken?

I wonder if I could just buy a new controller board and install it myself...since I would just have to duplicate the wiring I have now. Anyone else ever do this? Is it hard? Any idea how expensive a new board would be?

Thanks