This morning I found that a bedroom TV and STB would not receive signals from the Sat dish.
Lounge TV and STB worked ok.
With the lounge STB running the bedroom STB would receive TV ok.
Taking the bedroom STB to the lounge - received TV ok.
My conclusion is lost DC connection and/or pass though with the Splitter on the bedroom coax.
Somewhere under my wooden house floor there is a splitter.
Have been in my house 6 years and bedroom STB has always worked until now without any other STBs running.
Before I squeeze myself under the floor for a look, I might buy a spare splitter from Jaycar (about $15).