Sometimes award availability opens close to the day of travel, anytime within the last two weeks or so if a flight isn't selling very well. Consider looking for an A fare, taking low coach and hoping for a free upgrade, or looking for connections using routings with easier availability. Flights at inconvenient times are more likely to have low award seats, including very early in the morning or very late at night (i.e., departure too late for dinner and arrival around midnight).