Apple TV Invisible to iTunes?

Okay, so this has been bothering me all week and I can't seem to work out what's going on. My Apple TV isn't letting me airplay anything from iTunes and it won't connect to my Home Sharing either. Here's the weird part though. I have two other Apple TV's in the house and in iTunes, they are listed under the Apple TV icon dropdown selection as something I can airplay to. Just not the one I want to stream to (same thing with my iPhone). However, if I go to the control bar at the top of my screen and click on the Apple TV icon for screen sharing/mirroring, the third Apple TV shows up (the one I do want to connect to). It was working one night and then when I woke up, it just wasn't. I've never been so confused with an Apple product before.

What I've tried:

• Zapping the PRAM
• Restarting the computer and Apple TV
• Restoring the Apple TV
• Turned on/off Home Sharing in iTunes/Apple TV
• Signed in/out of iTunes Store on both devices
• Changing the computer name in System Prefs/Sharing

Apple TV: A1469 running v7.2 (7512)

Macbook Pro: (mid 2014) running El Capitan (10.11.3)

Any help would be greatly appreciated.

Cheers