I've been using a TV connected to ATV2 to show presentations in my office via airplay from my Mac. The ATV2 is on a wireless network using a express router and the mac is connected to the same network on the same router. I see today that the airplay option is not showing up on the mac. The airplay is turned on on the ATV2 but the mac isn't seeing it. ATV2 has most recent update but mac is still on mountain lion. Any suggestions?