Good evening/night to Victoria from old Europe  ;)...
your video is very helpful - until now I didn't need to activate the avionics master with an default-flight-plane (in my cause EXTRA 300) and after that the selection/change to - in this cause - the BUFF.
Therefore I wondered about the right external indicator bulb (orange) stayed dark - now it is enlightened. Already a step forward..... . ;)
Otherwise - engines refuse revving..... . :-[
But - I don't give up - this problem is small in comparison with the annoying 4-GB "threshold".... - always named OOM.... . :-/