Hey scott,
3 things to try.
First, use FM, not NFM mode. I know the system is supposed to be NFM but FM works better for what we are trying to do, because this allows us to pull in transmissions that would normally be clipped by NFM mode.
Next make sure you have the right freq's. These are what I use:
PRWN CC A 867.21250 MOT 0.0 D
PRWN CC A 867.96250 MOT 0.0 D
PRWN CC B 867.08750 MOT 0.0 D
PRWN CC B 867.11250 MOT 0.0 D
PRWN CC B 867.93750 MOT 0.0 D
PRWN CC B 867.98750 MOT 0.0 D
PRWN CC C 867.97500 MOT 0.0 D
PRWN CC C 867.20000 MOT 0.0 D
PRWN CC D 867.75000 MOT 0.0 D
PRWN CC D 867.82500 MOT 0.0 D
PRWN CC D 868.27500 MOT 0.0 D
PRWN CC D 868.35000 MOT 0.0 D
PRWN CC E 867.13750 MOT 0.0 D
PRWN CC E 867.16250 MOT 0.0 D
PRWN CC E 867.35000 MOT 0.0 D
PRWN CC E 868.07500 MOT 0.0 D
PRWN SKYH IR 868.30000 MOT 0.0 D
PRWN SKYH IR 868.45000 MOT 0.0 D
Make sure you've set up the system as a motorola type 2 trunked system (I don't have a 396, so you'll have to check with your owners manual to see what the steps are) and then program these freq's into it.
Finally, turn the squelch as far down as you can before it opens . If all you intend to monitor is the PRWN system, turn it all the way down.
EDIT: One more thing, where are you located? If you are in Tempe or Mesa for example, you won't hear PPD 24x7 - you'll only hear them when one of them affiliates with the same control channel that you are on.
Hope that helps,
-AZ