This happen the other day to one of my teachers. She said she was using AIrPlay to mirror her iPad to her classroom AppleTV. It was working fine one day, then the next not so much. The Apple TV was working. It showed us the standard Apple TV start menu, but as soon as we turn on AirPlay mirroring on the iPad...the TV went to a black screen.
The frustrating part of this was that I was able to mirror; my iPad, iPod and my MacBook desktop using AirParrot. So my thinking was that it must be some settings on her iPad. I looked up this problem on the Apple tech support webpages and was told to do numerous things to troubleshoot and/or fix the issue.
1- Here's one real easy one to try first, shut down and restart your MacBook. NOT KIDDING!! I found that a lot of my teachers never turn off their laptops, after a while (my theory) it's resources run down to such a low level it can't "power" the video signal to the Apple TV. That's my theory and I'm sticking with it!
2- Apple suggested to; turn of the Bluetooth on the iPad, reboot my router/wireless access point, restart the iPad, then finally restart the Apple TV. We unplugged the Apple TV from the back of the box, waited 10 seconds and plugged it back in...et voila! I worked again. WHO KNEW???? Our techie knew about this fix because this same exact issue had happen with our principal's Apple TV. So before you go through all that rigor moral, just try unplugging and re-plugging.
3- Another fix I found to work was to update the software on the Apple TV. One of my teachers got the black screen when he updated his Mac to OS High Sierra, as soon as I updated the Apple TV everything came back.
