Mark,
Okay, this is what I found out:
Here is the States most of the satellite overlay information is on the Marine Charts and not on the Inland lake mapping cards. I don’t know how this works out in Australia but I would confirm that there is satellite overlay data on the map card you are using and that it is in the area you are looking in.
For the satellite overlay to show up a Tech here told me that you should set the Overlay Transparency menu all the way down to 0 (zero). Be sure that you are using the Chart View. Set the Platinum setting on Land and Water.
Try that and see what you get.