Spinning beach ball appears when I try to turn on AirPlay mirroring

Hi all

I have an Apple TV 3 and MacBook Air - all software is up to date. I've used AirPlay mirroring in the past with these devices but when I tried it today it wouldn't work. I click on the menu bar then click on Apple TV. A spinning beach ball appears for a few seconds on the Air and that's it - nothing on the TV and the menu options haven't changed.

I've also tried selecting AirPlay mirroring on in system preferences. Again, the cursor changes to a beach ball for a few seconds and the setting returns to "off".

Any suggestions?

Paul