4th gen TV will not recognise Home Sharing

I used to have a similar problem, but it was intermittent. Sometimes Home Sharing would work, other times it wouldn't. I had a guest network set up on my wi-fi. While my computer (with the iTunes library) was one my main wi-fi, sometimes the Apple TV would log into my guest network. The apple TV couldn't find iTunes so I got the message 'Home Sharing wasn't turned on'. I just got rid of the guest network and now no longer get that message.

Have the very same issue. Home sharing will work if the itunes PC and the ATV 4 are wireless. No issues. As soon as you connect up either with the ethernet connection....away it goes. Everything is on the same network so that is not an issue. I have looked at all the firewall stuff and router settings so that is not an issue. I feel the issue is with ATV 4 firmware. Someone at Apple must know what is causing this.

Norton needs to get its act together and stop messing up software thats working ok.

Don't hold your breath. Non-Apple "anti-virus" products serve no beneficial purpose on Macs, a fact Symantec is well aware of and has publicly admitted. If you choose to purchase their software in spite of that fact, they'll gladly take your money. Plenty other outfits will too. Read Effective defenses against malware and other threats.