I am presuming that if the laptop is working in a similar setup (own power) ignition or masters off in your car / aircraft. then the laptop has one of those pesky aircraft sensors that allows it to see out from under its lid and it says to itself "oh sh!t, I'm in an aeroplane - stop working"
Sorry but having read this thread (and agreeing with the many points regarding the wisdom of a laptop in an aircraft for filming) can't help but wonder if the OP is in fact a very clever and sophisticated, now whats the word? ah yes, troll....
There is no other logical explanation why the laptop should not work with the master off in the aircraft on the ground.
RyanRS said: "I did mention in my opening post that i was having these issues whilst even the master switch was off, so i was very much on the ground and parked in the apron whilst analysing the faults!"