1. Check whether other devices can connect to the wireless network.
2. If other machines can be connected, shut down the phone and restart it, go to Settings -WLAN Settings - Turn on the WLAN function again.
3. Go to Settings -WLAN Settings - Click the network you want to delete - Forget network\/Delete network, and then reconnect to the WLAN.
4. Check whether the DHCP function is disabled on the router. After this function is enabled, you can correctly obtain the IP address. Finally, restart the mobile phone and the Wi-Fi router