Q: restore apple tv - error 11

Restore to factory settings instead of using iTunes > Restore your Apple TV (2nd and 3rd generation)

If your Apple TV fails to restore through iTunes……..

• Check that you have correctly followed the instructions for your model of Apple TV.
• If not already, try using a powered USB port.
• Repeat the process but this time try connecting the cable while iTunes is closed.
• Repeat the process with another cable.
• Try restoring the Apple TV on another computer in another location.

As per Get help with iOS update and restore errors - Apple Support

Check for hardware issues

Errors: 1, 3, 11, 12, 13, 14, 16, 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 53, 56, 1002, 1004, 1011, 1012, 1014, 1667, or 1669.

Your device or computer might have a hardware issue that stops the update or restore from completing.

1. Check that your security software and settings aren't blocking your device from communicating with the Apple update server.
2. Then try to restore your iOS device two more times while connected with a cable, computer, and network you know are good.
3. Make sure that your security software and settings are allowing communication between your device and update servers.
4. If you still see the error message when you update or restore, contact Apple support.

If you still see the error message, check for outdated or modified software.

Make sure you have disabled any security apps on your Mac/PC and try it again.

Resolve issues between iTunes and third-party security software - Apple Support