WhatsApp for Samsung Galaxy Discover S730M

Samsung's battery optimization is the usual culprit, as it puts WhatsApp to sleep in the background and silences alerts. Open Settings > Apps > WhatsApp > Battery and set it to Unrestricted (on older One UI builds this lives under Settings > Device care > Battery > App power management, where you remove WhatsApp from the sleeping/deep-sleeping list). Then check Settings > Apps > WhatsApp > Notifications is on, and inside WhatsApp confirm Settings > Notifications has the right sound and that Conversation tones aren't muted. See how others solved this on Reddit

An app or system update often resets WhatsApp's notification channels, so re-enable them at Settings > Apps > WhatsApp > Notifications and turn each category (Messages, Group notifications) back on with sound and pop-up enabled. If the toggles look on but you still hear nothing, tap each notification category and re-pick a Sound, since updates can blank the assigned tone. As a last resort, clear the WhatsApp cache via Settings > Apps > WhatsApp > Storage > Clear cache and reboot to rebuild the notification channels. See how others solved this on Reddit

Go to Settings > Apps > WhatsApp > Notifications and switch Allow notifications back on, then enable the individual Messages and Group notifications channels underneath it. Inside WhatsApp itself, open Settings > Notifications and make sure Message notifications and Group notifications both have a Sound selected and the Vibrate option set. If a specific chat is silent, open that chat > tap the contact name > Custom notifications and uncheck Mute. See how others solved this on Reddit

Most reliability problems on Samsung phones trace back to aggressive memory management killing WhatsApp in the background, so first set Settings > Apps > WhatsApp > Battery to Unrestricted and disable any 'Put unused apps to sleep' option under Settings > Device care > Battery. Keep the app current through the Play Store, since Samsung's older Android base sometimes breaks with outdated WhatsApp builds. If it stays buggy, clear the cache at Settings > Apps > WhatsApp > Storage > Clear cache (this keeps your chats) before considering a reinstall. See how others solved this on Reddit

Delayed batches mean the system is throttling WhatsApp's background activity and waking it only periodically. Fix this by setting Settings > Apps > WhatsApp > Battery to Unrestricted, and turn off Settings > Connections > Data usage > Data saver restriction for WhatsApp so it can sync in real time. Also make sure WhatsApp isn't in the sleeping-apps list under Settings > Device care > Battery > App power management, which is what causes alerts to pile up and arrive together. See how others solved this on Reddit

The watch only mirrors alerts that actually fire on the phone, so first confirm WhatsApp notifications work on the S730M itself via Settings > Apps > WhatsApp > Notifications. Then open the Galaxy Wearable app on the phone > Watch settings > Notifications, enable Notifications, and make sure WhatsApp is ticked in the app list. If alerts stop when the phone screen is on, enable 'Show notifications on watch even while using phone' inside that same Galaxy Wearable notifications menu. See how others solved this on Reddit