Some WhatsApp users report that they are unable to connect to WhatsApp. This problem probably may be the outage of WhatsApp at 6 pm on 17 May 2017. If you still have this problem after that, the fault may lie elsewhere.
If you can’t connect to WhatsApp, this is usually because you don’t connect your phone to an active internet. Then you should check whether you can browse any web pages on your phone. Otherwise, connect to other active internet services.
If you are unable to go online at all, then there are still some things you can have a try.
Step 1: If You Are Using WiFi
Please switch the WiFi connection on and off, or put the phone into Flight mode and remove it out. Or try to restart your device, and then check whether your WhatsApp can connect to the internet.
Also ensure your device keeps WiFi on during sleep, to set it to Always by going to Settings > WiFi > Advanced. If the above methods not work, try to restart your wireless router.
Step 2: If You Are Using Cellular Data
Make sure your mobile data connection is turned on, and your phone has sufficient signal. And check whether you have restricted background data usage for WhatsApp in the Data Usage menu.
If you can use WhatsApp over WiFi but not over with your cellular data, it is mainly because the APN setting doesn’t allow non-web traffic, then check with your phone carrier.
Step 3: Downloaded the Latest WhatsApp
Check for WhatsApp updates on your Android by opening Google Play and taping the three lines at the top left and choose My Apps. Then checking the Install tab to see whether there is an update available for WhatsApp.
As for iPhone, open the App Store and tap the Updates icon to make sure that you have downloaded the latest updates for WhatsApp.
Note: If you reinstall WhatsApp but forget to make a backup of your WhatsApp chat history in advance, here is what you can do to recover lost WhatsApp chat history from Android phone.
Step 4: If Still Not Working...
If your WhatsApp is still not working, try to uninstall and reinstall it.
Please note that you need to backup all your WhatsApp data on your Android/iPhone , otherwise you will lose all your WhatsApp history. You can backup WhatsApp with its built-in backup feature, to do that please go to Settings > Chats > Chat Backup, and tap Back Up, then your WhatsApp conversations will be stored on your phone memory or Google Drive.
This is of your choice.