Airplay Icon missing from menu bar

Hi,

I have a Macbook Pro late 2013 & previously I was apple to mirror to my Apple TV using the airplay icon in the menu bar. This icon now seems to have disappeared and I am wondering if this is since the upgrade to 10.9.4 (first time trying to mirror since updating). When I go into system preferences > displays, airplay display shows: no devices detected. Show mirroring options.... box is ticked.

I have rebooted router & Apple TV and also reset the Apple TV but no change. I can stream via airplay to the Apple TV fine, it is just the icon that is missing in the menu bar.

I am using a 15" MacBook Pro 2.3Ghz late 2013 & Apple TV 3.

Anyone else had this issue or can suggest anything?

thanks.