Q: Apple TV cannot connect to iTunes library on MacBook Pro after upgrade to Yosemite/iTunes 12

Worked for me too.

I have been battling with this problem since I updated my early 2011 iMac to Yosemite. My late 2014 macbook pro has not had this problem at all. I tried all sorts of things and nothing worked until today. I renamed the iTunes library under preferences in iTunes and immediately home sharing to my Apple TV3 started to work again. Hopefully this helps.

That worked. Finally! Thanks so much!

Use your Apple TV connection to your TV screen or monitor.

Setting>General>Network>Wireless Configuration.

Check you have a connection (bar strength).

Re-input your Wi-Fi connection passcode

My Apple TV (3rd gen) would not connect to the library on my iMac which connects to the apple tv via WIFI.  The AppleTV is hardwired to my Mac Pro tower and to the router and they see each other fine.  I tried starting everything including the router, apple tv and computer all to no avail.  I tried turning off home sharing from the iMac and changed the name on the iMac from the sharing systems pref.  Nothing. 

I turned off home sharing on the Apple TV and then went back to the computers icon on the Apple TV.  The Apple TV asked if I wanted to turn home sharing on, I clicked yes and it worked.

Thanks... It helped...!!

I'm new to posting on this forum and was having trouble seeing my iTunes Library. After hours of searching different forums and threads, trying just about everything others had tried with no luck, I called Apple Support. It was as easy as turning off my firewall on my virus protection software.

No charge, no hassle and now watching a movie I've been wanting to watch. I hope others have the same luck I did or at least try calling Apple before pulling your hair out.

Virus protection software causes more issues than it actually solves. I've had Macs since 1998, no viruses ever (no virus protection). OS X is based off a proprietary/UNIX core that has virus protection built in. A Mac cannot be infected with a virus. Now, if one is booting windows off a Mac machine, they will want virus protection for the windows side of things, but, any virus would only affect windows, not OS X. (malware and phishing are not the same as a virus and cannot take down your Mac.).

I had this problem until I turned off everything including computers, router, base station, time capsule, apple TV, the whole works. Turned it all back on after 1 minute and everything is working fine now and everything connects with Apple TV as it was before the upgrade to Yosemite. Happy at last

I got this solution from another post so sharing here.

Home sharing is done from two place in iTunes.  Yes two, don't ask me why:

1.  iTunes/Preferences/Sharing/ then click on sharing

AND

2. Go into iTunes, click on File/Home Sharing and turn it on (will ask for your iTunes username and password

That solved it for me.  Hope it works for you too.

Fantastic, this worked for me, I've been pulling my hair out with this issue for weeks.  Thanks for your advice.

I also renamed the Library name in iTunes. iTunes > Preferences > Library Name

I received an email from Netgear notifying me that there was an update available for my R7000 router.  In the update notes it identified a fix for a problem with iTunes 12.1.  After I applied the fix my 4 ATVs were able to communicate with my iTunes library much more reliably, but I still experienced occasional problems.

I decided to install a small switch in to connect to all of my ATVs and my iTunes library and then connect that switch to my router.  This appears to have fixed my problem. 

It has be 18 days since I made this network change and I have not had a single problem connecting to my iTunes library from any ATV or other device.

Thank you to itwatchdog. This solution worked for me. The situation was so frustrating!

THANK YOU MarkBennett221! I have been trying everything for hours, including changing my computer names, logging in / off, the PRAM solution, re-setting ATV, fiddling with the different home sharing options, and nothing worked. As soon as i turned my firewall off, bam, i could see my computer files on my ATV. A very simple fix.

Thanks again