sky9: from what I read (I don't know about that), I understand that RAT extends (and APU starts) if both AC transfer buses lose power in flight (even with engines running). That could be from failures or if both general switches (and both backup generators switches?) are switch off.
Propduffer: the log-on sequence could not be from power failure. It could only happen from power recovering (if the lost was from an electrical "problem"). Nobody knows for how long the SATCOM was unpowered (or not functional) because there was no communication at all between 17:07 and 18:25. The non-response to a request at 18:03 proves that the link was not functional around this time. This doesn't prove that the link was out of order all the time between 17:07 and 18:25.
Could someone confirm that the cockpit door cam is on the same electrical bus that the IFE?