Please check the satellite cable to see if it is connected properly from the room to the satellite dish, there might have been a disconnection when the previous owners moved their SKY box out.
The SKY LNB has a dual-feed of the Freeview Satellite and another backup satellite which contains no Satellite channels, the receiver should automatically pick up the Freeview feed (Optus D1) without any technical expertise.
But the possible cause is the LNB itself (The machine at the front of the dish) Older SKY LNB which looks like the one below:
This may need replacing as the older SKY LNBs have been reported in recent years that they need to be replaced with new machines, you can get LNBs at most aerial/electrical outlets or for a good price on TradeMe.
Let us know how you get on?
Dish TV Online Support