Resolution
First, sync your iPhone or iPod touch to iTunes in order to backup your user info, Contacts, Calendar, and other data. Then, try the following steps in order.
Step One
On the device, tap Settings > General > Reset > Reset Network Settings. Check to see if the device now displays the Wi-Fi address (tap Settings > General > About and scroll down to Wi-Fi Address). If there is a Wi-Fi Address, then you're done with these steps and can resync your settings and your media using iTunes.
If there's still no Wi-Fi Address, then continue to Step Two.
Step Two
On the device, tap Settings > General > Reset > Erase All Content and Settings. Check to see if the device now displays the Wi-Fi address (tap Settings > General > About and scroll down to Wi-Fi Address). If there is a Wi-Fi Address, then you're done with these steps and can resync your settings and your media using iTunes.
If there's still no Wi-Fi Address, then continue to Step Three.
Step Three
1. Restore the iPhone or iPod touch software (this erases all data on the device) using iTunes (see article 305744 for additional assistance).
2. After the restore is complete, sync your previous settings (mail settings, text messages, notes, call history, contact favorites, etc.).
3. Now verify if your device shows a Wi-Fi address (tap Settings > General > About and scroll down to Wi-Fi Address).
If there is a Wi-Fi address, then you're done with these steps. If there is no Wi-Fi address, then continue to Step Four.
Step Four
If there is no Wi-Fi address listed after doing the above steps, then your iPhone or iPod touch may need to be repaired. See the iPhone Service FAQ or iPod Service FAQ for additional service information.