I can't use Wi-Fi - Apple iPad (4th generation) (iOS6)
Cause 6 of 6: The Wi-Fi network is using a hidden SSID
If the Wi-Fi network is using a hidden SSID, you can't find the Wi-Fi network when you search for available Wi-Fi networks. You can only access a Wi-Fi network that uses a hidden SSID if you know the correct SSID.
Solution: Key in SSID and security settings manually on your tablet.