Same here. Trying to add a SYD-AKL flight in March 2016. QF flies 5x/day - the tool insists the only available flight is a LAN flight. Similarly adding PHX-ANC -- this is an (old) US Air flight (now AA) that is flown year-round - the tool insists there are no flights. In both these cases, if you simply do a flight search from the oneworld homepage, the flights show up fine. As is, the tool is useless....
Same here; very frustrating. I use the 'offline' tool, the OneWorld Timetables, to search for available flights/routing. They can be imperfect too, but at least you have a guide to flights.