You need to check that your phone is connected to the internet. You can do this by opening any browser on your phone and going on a website. If this doesn’t work, please read the following:connection troubleshooting steps.
If you have internet connection and your browser works perfectly, but you’re still experiencing issues with WhatsApp, you need to contact your mobile provider and system admin. Also, you need to make sure that your APN and router are configured to enable non-web and socket connections. Another thing you can do is change your connection. For example, if you are connected to mobile data, try connecting to Wi-Fi or vice versa instead.
Please make sure that Auto-sync data is turned on. To check this, go to Settings app > Data usage > Menu icon > auto-sync data.
Wi-Fi optimization needs to be turned off. Go to Settings app > Wi-Fi > Menu icon > Advanced > Wi-Fi optimization.
Make sure that Do not disturb is turned off. Go to Settings app > Sound > Do not disturb.
Check that all WhatsApp's permissions are granted. Go to Settings app > Apps > WhatsApp > Permissions.
If you’ve done everything mentioned above and still facing issues, it might be that you’re not receiving updates from Google’s push notification service. Also, the aforementioned steps do not guarantee that the integration will work perfectly.