WhatsApp for Samsung Galaxy Win Pro G3812

WhatsApp creates its own notification channels in Android, so the master toggle inside WhatsApp isn't enough. Go to Settings > Apps > WhatsApp > Notifications, open the Message notifications and Group notifications categories separately, and set each to Alert (not Silent) with a sound selected. Also confirm the channel's sound isn't set to None and that Do Not Disturb isn't active in the quick-settings panel. See how others solved this on Reddit

The pop-up (heads-up) banner is tied to notification importance, which can quietly downgrade after an app update. Go to Settings > Apps > WhatsApp > Notifications > Message notifications, set it to Alert, and turn on Pop-up so it appears at the top of the screen. In the same WhatsApp app settings make sure Allow notifications is on, and check that the app isn't being put to sleep under Settings > Battery and device care > Battery > Background usage limits (remove it from Sleeping/Deep sleeping apps). See how others solved this on Reddit

Group notifications are a separate channel from one-to-one chats, so you can quiet them without losing personal messages. Inside WhatsApp open the group, tap its name, choose Custom notifications or Mute, and silence it. To mute all group activity at once, go to Settings > Apps > WhatsApp > Notifications and turn off the Group notifications category. You can also long-press one of those notifications when it appears and turn off that category from there. See how others solved this on Reddit

This is almost always battery optimization killing WhatsApp in the background. Go to Settings > Apps > WhatsApp > Battery and set it to Unrestricted, then under Settings > Battery and device care > Battery remove WhatsApp from any Sleeping or Deep sleeping apps list. Finally, under Settings > Apps > WhatsApp > Mobile data, make sure Allow background data usage and Allow data usage while Data saver is on are enabled so messages sync while the screen is off. See how others solved this on Reddit

Samsung's aggressive One UI battery and memory management is the usual cause, since it puts idle apps to sleep to save power. Keep WhatsApp in memory by opening Recents, tapping the app icon at the top of the WhatsApp card, and choosing Keep open, then set Settings > Apps > WhatsApp > Battery to Unrestricted. After any major Android or WhatsApp update, recheck these settings because updates often reset them. See how others solved this on Reddit

A reliable reset is to rebuild WhatsApp's notification channels. Go to Settings > Apps > WhatsApp > Notifications, toggle Allow notifications off and back on, then Force stop the app via Settings > Apps > WhatsApp > Force stop and reopen it. If it still misbehaves, reinstall WhatsApp from the Play Store (your chats restore from your Google Drive backup), which recreates fresh notification channels with correct defaults. See how others solved this on Reddit