Q: Airplay mirroring doesn't work?

Hello,

I have a MacBook Pro from late 2011.

Yesterday i've updated my MacBook Pro to Mountain Lion.

I wanted to test the airplay mirroring but if I click om the airplay button on the top it doesn't recognize my Apple Tv (2).

If I try it on my iPhone 4s it does recognize my Apple Tv (2) and if I try to mirror my iPhone 4s on my Apple Tv (2) it does work.

Please, can anybody help my?

Thanks,

NLPindakaas

Here a picture what it looks like:

(It is in Dutch because I'm Dutch )