My Apple TV only plays audio when I try to play full screen video from my MacBook Pro. I recently wiped and reloaded all my MacBook software and it is updated. My Apple TV is on automatic update. Help?

My Apple TV only plays audio when I try to play full screen video from iMovie on my MacBook Pro. It wasn't always this way but I recently wiped my computer and reloaded everything back on. Both Apple TV and MacBook Pro software are up to date. I can make Airplay initially work (as it will show my computer screen) but when I try to play full screen it seems to freeze the video but audio continues playing through the TV. Help?