Still not working. My TV will not allow me to update. I've restarted it and that still doesn't allow me to update. Software on my computer has been updated. This morning my AirPlay icon was not available, then several hours later it was available, then I went to my TV to see if I could update the software and it did not allow it and it also caused the icon to disappear on my computer and it can no longer find my network. This never happened for the first year I had AppleTV. Now over the past month I'm having this problem. What changed?
Welcome to the Apple Community.
Intermittent problems are often a result of interference. Interference can be caused by other networks in the neighbourhood or from household electrical items.
You can download and install iStumbler (NetStumbler for windows users) to help you see which channels are used by neighbouring networks so that you can avoid them, but iStumbler will not see household items.
Refer to your router manual for instructions on changing your wifi channel or adjusting your multicast rate.
There are other types of problems that can affect networks, but this is by far the most common, hence worth mentioning first. Networks that have inherent issues can be seen to work differently with different versions of the same software. You might also try moving the Apple TV away from other electrical equipment.
The following article(s) may help you.
Wifi Diagnostic Software (for Mac users)