Notification problems can come from the app, the phone operating system, Focus/Do Not Disturb settings or battery restrictions. Start by checking whether messages arrive when WhatsApp is open.
Check system notification permission
Confirm that WhatsApp is allowed to show notifications in the phone’s system settings. Then review whether sounds, banners or lock-screen notifications are disabled.
Review Focus or Do Not Disturb
A Focus mode can silence notifications even when WhatsApp itself is configured correctly.
Check battery and background restrictions
Some Android devices apply aggressive background limits. Use the phone manufacturer’s normal settings to allow messaging apps to receive messages in the background.
Update carefully
If the issue started after an app or operating-system update, check for a newer bug-fix update and restart the device before reinstalling.