The exact cause and circumstances of a five-day outage that blocked nearly half the state’s lottery retailers from selling printed tickets like Pick-3 and Mega Millions earlier this month are still a mystery, but a few determinations are unanimous. The blackout, although anomalous, was unacceptable, may have been detected sooner and should have been handled better, state officials and executives from Northstar New Jersey, the group responsible for the lottery’s sales and marketing, said at a meeting Thursday.