To ensure fast delivery of messages and WhatsApp notifications, the phone must be configured correctly.
Make sure your phone has an Internet connection
To check it out, open a browser and access a website. If it does not work, try following these steps.
If the webpage works but WhatsApp does not, contact your mobile operator and system administrator and make sure your APN and router are properly configured to allow socket and non-web connections. Also, try a different network. If you are connected via Wi-Fi, try a cellular data network and vice versa.
Make sure there are no restrictions on background data
Open Device Settings> Apps> WhatsApp> Data Usage.
Make sure the Limit app data in the background option is not selected.
Repeat the previous steps for Google Play services.
Other resolution options
Restart the phone, or turn it off and then on again.
Reset your app preferences by going to Device settings> Apps> Menu button> Reset app preferences.
Be sure to leave the phone connected to a power source to prevent the power save mode from activating.
Exit from WhatsApp Web by going to WhatsApp> Menu button> WhatsApp Web> Disconnect from all the computers.
Make sure that Wi-Fi is enabled during suspend by going to Settings> Wi-Fi> Settings icon> Keep active Wi-Fi during sleep> Always.
Uninstall any killer task. These applications prevent WhatsApp from receiving messages when you’re not using them.
Launch the Hangout app and sign out of all accounts. Then, launch Hangout again and sign in to all accounts again.
Device specific instructions Android 4.1 – 4.4
Make sure that Auto-sync data is enabled in Settings> Data Usage> Menu button> Auto-sync data.
Make sure the Optimize Wi-Fi feature is not selected in Settings> Wi-Fi> Menu button> Advanced> Wi-Fi optimization. Android 6.0+
Make sure the Do not disturb option is disabled or that you have authorized WhatsApp notifications in priority mode under Device settings> Audio> Do not disturb.
Make sure that all WhatsApp permissions are enabled in Device settings> Apps> WhatsApp> Permissions.
If all the above steps do not help you, you may not receive updates from Google’s push notification service.
Save your WA, please!
This one from smarty...
And make sure that next time you'll take care of your phone's settings without being distracted by communications from friends who only engage in drinking, having fun, and making fun of those who are equal to themselves.