No Internet access when switching networks wifi fixes for your iPhone

If you are switching between different Wi-Fi networks and you are unable to access the Internet on the iPhone or perform other data activities thru Wi-Fi, try turning Airplane Mode on and then off (tap Settings and turn Airplane Mode on and then turn Airplane Mode off). For iPod touch, turn Wi-Fi off and then back on again (tap Settings > Wi-Fi and turn Wi-Fi off and then turn Wi-Fi on). If the issue continues, tap Settings > Wi-Fi > Other (under Choose a Network) and then enter the Wi-Fi Network Name (SSID) and select your Security setting and enter your password.

If you are receiving the error message "Unable to Join Network Failure (error -3)" on the iPhone or iPod touch try this

Unable to Join Network Failure (error -3)" connecting to Wi-Fi
verify your Wi-Fi Network Name (SSID) and Security setting (WEP password, WEP hex or ASCII, WPA, or WPA2) for the device.

On the Wi-Fi Access Point/Router, you should verify if MAC address filtering is turned ON or OFF on the router, whether the security settings on the router match the iPhone or iPod touch (WEP password, WEP hex or ASCII, WPA, or WPA2), and try disabling (QoS) quality of service if that feature is turned ON for the router.

If you are still receiving the error message "Unable to Join Network Failure (error -3)" on the device when attempting to connect or join to your Wi-Fi network after trying the above suggestions, tap Settings > Wi-Fi > Other (under Choose a Network) and then enter the Wi-Fi Network Name (SSID) and select your Security setting and enter your password.

Weak iPhone Wi-Fi signal Fix

If you are having issues using the Internet, checking email, checking stocks, or other data activity with the iPhone (the possible error message could be "could not connect to server") and the Wi-Fi icon is showing very weak signal, try turning Wi-Fi off on the device so that the iPhone can use EDGE (tap Settings > Wi-Fi and the set Wi-Fi to off).