You say you have a 4S, and you are upgrading it? There is no update available for the 4S yet, so I'm not sure what you mean by "after a failed update". Putting that asside, however -
Well, the error and the failed update are probably related. What was the error when the update failed? Here is what Apple says about that error:
Essentially, iTunes could not contact Apple's activation server (gs.apple.com). There are a couple of possibilities:
- Your antivirus or firewall blocked the conntect.
- Your router blocked the connection.
- You have a redirect in your "hosts" file for gs.apple.com
You didn't say what your computer or operating system is, but to fix the last of these you need to edit your hosts file and remove any lines that contain gs.apple.com.
The file is located in /etc/hosts on a Mac, and c:\windows\system32\drivers\etc\hosts on Windows.
BTW, if gs.apple.com is found in your hosts file it means your computer was used to hack some iDevice at some time in the past, and not necessarily the device with the problem.