1st gen Apple TV not in devices list in iTunes

My 1st generation AppleTV is no longer showing in the devices list in iTunes on my Mac Pro. I have read several pieces of advice and performed the following long list of actions but I am still stuck and unable to sync my Apple TV. I hope someone has a new suggestion for me?

The AppleTV has had the computer removed from the connections setting. It has been rebooted and left on the connect a new computer screen with the numerical password visible.

The AppleTV can be seen visible in the iTunes of my Macbook Air running 10.8.3 and the iTunes version is 11.0.2. I have not 'clicked to setup' since my main library is on my Mac Pro that used to sync. I can ping appletv.local from my macbook air succesfully which returns an IP address.

My MacPro is running OSX 10.7.5 and iTunes 11.0.2 and one day the device failed to show in the devices menu. I cannot ping appletv.local from my Mac Pro but I can ping the IP address returned from the ping on my Macbook Air.

At first I removed the device from iTunes preferences and removed the computer from the AppleTV which allowed me to see the AppleTV on my Macbook Air but not my Mac Pro.

Secondly I used AppZapper to uninstall iTunes and reinstalled from a fresh download as r4ecommended here -> http://reviews.cnet.com/8301-13727_7-10329494-263.html I also used Pacifist to reinstall the Apple Mobile Device Service after removing the service as per the instructions here -> http://support.apple.com/kb/HT1747 My iTunes library is back as it was but my other devices were originally missing until I connected them via USB to re-enable the wifi sync.

I can see my shared libraries between my MacPro and my Macbook Air. I can also use Airdrop between them and can connect between them as usual. I have disabled the firewall on my Mac Pro just in case and I have no VPN or antivirus software that blocks any communication.

My network setup is a little unusual since I have my ISP router as the DHCP assigner connected to an Airport Extreme base station that acts in bridge mode to distribute a wifi network across my home. I then have a powerline adapter connected to the airport base station to send network around my home to places where wifi is weak. My macbook air connects to the wifi. My MacPro connects via a switch in my office to a 2nd powerline adapter. My AppleTV connects via a 3rd powerline adapter and can see the internet fine (it plays youtube videos for example). None of the network devices have any ports blocked on them and since the Macbook Air connects to the AppleTV as expected but the MacPro does not then I do not think it is network related.

So I can only assume there is something wrong with my MacPro being unable to recognise my AppleTV as an AppleTV rather than just another device on my network. Anyone else got any ideas of what to try on my MacPro to get it to recognise the AppleTV?