Restore activation stuck/BRICKED ATV3
Restored ATV gen 3 stuck on Activating...date and time. Did full USB restore from iTunes but still can't get beyond Date and Time.
AppleTV 2, Windows 7, Stuck in activation
Be sure your router does not block UDP connections on port 123, NTP. ATV needs that to set the time. Look in your router settings for "Protocols". It's likely in the Advanced section, pretty far down.
Some users have worked around this by using their iPhone to create a temporary personal hotspot and configuring ATV with that. Then they change network settings to use their normal WiFi. Obviously, this requires that your mobile servise includes the personal hotspot feature.