ATV won't connect to iTunes after switching computers

I recently switched my iTunes library to a new computer and now ATV won’t show up in the devices drop down when I open iTunes. I have tried everything, I have look for ATV’s enabled, I have the newest ATV flash software, I’ve tried rebooting, reinstalling itunes, unplugging the router. Is there something else I can try?

This is from the Apple website. There has been an ongoing problem with Apple TV not showing up, especially with Windows. I ran into it to, hence me buying ATV Flash. I think what you ran into is: “If you have configured Apple TV to stream from another iTunes library, Apple TV won’t be available in iTunes”. Check out that section

Good luck.

Resolution
First steps
Verify that you have the latest version of iTunes installed.
Verify that you have the latest version of Apple TV software installed.
If you’re using Mac OS X v10.6 (Snow Leopard), make sure that you have Bonjour Update 2010-001 or later installed. (You need to restart the computer after installing this update for it to take effect.)
Verify Apple TV is powered and properly connected to your television and you can navigate the Apple TV interface.
Verify Apple TV is properly connected to your network and the network is properly configured. When configuring Apple TV, if you do not see your wireless network, exit the selection screen by pressing the Menu button then go back in and the software will rescan.
You can’t stream and sync from different computers at the same time. If you have configured Apple TV to stream from another iTunes library, Apple TV won’t be available in iTunes. Go to the Sources menu on Apple TV and select the computer you’re trying to sync from.

I reset ATV to factory setting and the new computer now recognized it, but when I reinstalled ATVflash the computer no longer recognized it, what should I do now? Seems like its an ATVflash problem.

There is a guide for getting iTunes to recognize the AppleTV here: http://support.apple.com/kb/TS1453