wash seems in generel to have issues, not only on N9. But, again, I repeat, this is not a stable monitor mode. Still seems to 'loose' wifi connection when enabled (airmon-ng). As you figured out, opening the network applet and letting the N9 search for accesspoint seems to again activate the wlan0. Also, I am afraid, it seems that TX power is rather weak. Meaning that we will need to be in proximity of accesspoints to be cracked.