airplay won’t play on your laptop? here’s your problem

Mac airplay is awesome and has really helped us in meetings. We connected an apple TV to all of the projectors and whoever is speaking, if they have relevant content, just grabs the screen wirelessly. No more plugging in monitor cables etc. But as luck would have it today airplay worked on everyone’s laptop EXCEPT mine. It’s not like I’m always messing with my hardware configuration or anything (cough).

Anyway, here is your problem if you are faced with the same issue. I had moved my menu bar to my larger desktop monitor at work so it was my primary when I plugged in, but reverted to my laptop when I wasn’t connected. Works great. One catch – airplay won’t work in this configuration on Mac OS X 10.8.2. In short:

This does NOT work with airplay:
display preferences dialog box

This is the part that is wrong:
this is wrong for airplay

And this is how it needs to look for Airplay to work with the Macbook Air and Apple TV in Monitor Preferences on Mountain Lion.
this is right for airplay

Your welcome. Because that was a real pain to figure out. No errors, it just wouldn’t connect and kept prompting for the password for the Apple TV then dropping back to the “Airplay Off” setting with no further error message. Hopefully this saves someone else some time.