It can be annoying when the wireless internet stops working on your iPhone, iPad, or iPod touch. However, there are just a few steps that can allow you to get the Wi-Fi working on your iOS device again.
Step 1: Reset the Wi-Fi on your Device
Open the Settings app on your iOS device. From the main screen, select Wi-Fi. If the switch at the top is in the off position, turn it on. If it is in the on position, switch it off and let go, then flip it back on. If your problem is not resolved, move to step 2.
Step 2: Forget Network
Still on the Wi-Fi settings screen, find your wireless network name and press the blue arrow to the right of it. Press "Forget this Network" at the top and go back to the Wi-Fi Networks page. Press your network name again. You may have to re-enter your password and any Static IP settings that you may have entered before. If your problem is not resolved, move to step 3.
Step 3: Reset Your Router
Unplug your wireless router and modem (if you have them). Allow them to be unplugged for a few seconds, then plug in your modem first (if applicable) and allow it to fully load. Then, plug in your router and allow it to load. If this doesn't resolve your problem, move to step 4.
Step 4: Check Your Connection
Check that your internet connection works on another device. If it does not, you may want to contact your ISP's support. If your connection does work on another device, move to step 5.
Step 5: Last Resorts
At this point, you have three options. The first is to contact AppleCare, but this is only an option if you purchased AppleCare for your device. The second option is to make an appointment at Apple's Genius Bar. The third option is to restore your device with iTunes and get a fresh start.