airplay icon disappeared from my macbook air

I use a MacBook Air 11 - OS X Yosemite 10.10.3. I have an AppleTV working on other devices. But the icon to connect my Air to the TV has disappeared.

I tried everything I could find online, from restoring the AppleTV to restarting the router. It works on other devices, so I dont think its a problem with the AppleTV.

I tried the firewall settings but nothing seems to work.

Please help.

Thank you