January 2018 is a very peak season for travel, and being that it’s only 4 months away now it wouldn’t surprise me if there weren’t any seats available. Airlines won’t necessarily make seats available on all flights or on all days, and when you’re flying in peak season you’ll generally find award seats hard to come by unless you’re organized and booking 11 months out as the airlines know the demand is there that these seats will go for cash if they just wait.
Also JAL don’t fly to Munich, meaning any award space you did get hypothetically would take you AUS - TYO - HEL - MUC or AUS - TYO - LON - MUC with Finnair or BA respectively, being the oneworld partners in the region to take you the rest of the way.
That being the case, the BA website might also show no availability if one of the connecting flights didn’t have any seats, so you could potentially change your search to be Sydney - Tokyo - Europe (one of the cities JAL do fly to), and see if that opens anything up? If you could get the long-haul flights on points and then pay cash for an intra-europe flight, I’d call that a win.
Hope that helps!