Part 1: Basic Solutions on Your iPhone
Part 2: Contact the Wireless Carrier
Part 1: Basic Solutions on Your iPhone1. Upgrade WhatsApp: Make sure your WhatsApp has been upgraded to the latest version. If not, go to App Store and download the newest WhatsApp.
2. Restart your iPhone: Long hold on the power button until the note "slide to power off" occurs. Slide the button to power off your iPhone. After that, reboot your device.
3. Go to "Settings" and turn off the Airplane Mode if it is on.
4. Go to Settings > General > Reset > Reset Network Settings. (This will delete all your saved Wi-Fi passwords.)
5. Uninstall the WhatsApp and then reinstall a new one. (Note that this will clear all your chat history. Before that, please back up your WhatsApp message from iPhone by following the command line: Go to WhatsApp Settings > Chat Settings > Back Up Now.)
6. Upgrade your iOS to the newest version. (Before upgrading, back up your iPhone with iCloud and so that you can restore your phone after that.)
Part 2: Contact the Wireless CarrierIf your use a unlocked iPhone or a pre-paid SIM card, you need to adjust APN settings in your iPhone. Please contact your wireless carrier and ask for a detailed guide to do that.
Some public network such like Captive Wi-Fi network at the airport, hotel, etc. requires users to log in before connecting to the network. If you are failed to connect your WhatsApp to Internet, check whether your iPhone is online or not by opening a webpage on Safari.
If you are using a campus or corporate Wi-Fi, your iPhone may be blocked by the firewall restriction. Turn to the network administrator. When using WhatsApp, turn off proxy or VPN service.