WhatsApp for Nord CE 3 Lite

This usually happens when OxygenOS's aggressive battery management freezes WhatsApp in the background. Go to Settings > Apps > App management > WhatsApp > Battery usage and set it to 'Don't restrict' (and enable 'Allow background activity'). Then make sure WhatsApp is updated to the latest version from the Google Play Store, since outdated builds can stop syncing. If it still fails, clear WhatsApp's cache under Settings > Apps > App management > WhatsApp > Storage usage > Clear cache and reboot. See how others solved this on Reddit

Delayed messages are caused by OxygenOS killing WhatsApp's background connection to save power. Go to Settings > Apps > App management > WhatsApp > Battery usage and choose 'Don't restrict' plus 'Allow background activity'. Then disable 'Sleep standby optimization' under Settings > Battery > More settings. Locking WhatsApp in the Recent apps list (open Recents, tap the app's menu or hold the card, and tap the lock icon) also stops the system from clearing it. See how others solved this on Reddit

When this only happens on mobile data, OxygenOS is restricting WhatsApp's background data. Go to Settings > Apps > App management > WhatsApp > Data usage and enable both 'Mobile data' and 'Background data', and turn off 'Disable data when Data Saver is on'. Also check that Data Saver isn't blocking WhatsApp under Settings > Connection & sharing > Data usage > Data Saver. Finally confirm notifications are allowed under Settings > Notification & status bar > Manage notifications > WhatsApp. See how others solved this on Reddit

After an OxygenOS security patch, WhatsApp's camera permission can get reset or the camera process can get stuck. Go to Settings > Apps > App management > WhatsApp > Permissions and re-grant 'Camera', then clear WhatsApp's cache under Storage usage > Clear cache. If it still shows a black screen, reboot the phone to release the camera from any app holding it, and update WhatsApp from the Play Store. See how others solved this on Reddit

Incoming WhatsApp calls fail to wake the screen when full-screen notifications are blocked. Go to Settings > Apps > Special app access > Display over other apps and enable it for WhatsApp, then open Settings > Notification & status bar > Manage notifications > WhatsApp > Calls and turn on lock-screen notifications and 'Banners'/heads-up display. Also set WhatsApp's Battery usage to 'Don't restrict' so calls aren't suppressed in the background. See how others solved this on Reddit

Brief freezes on incoming WhatsApp notifications are usually tied to a corrupted notification cache or a heavy custom notification tone. Clear WhatsApp's cache under Settings > Apps > App management > WhatsApp > Storage usage > Clear cache, and switch to a default short notification sound in WhatsApp > Settings > Notifications. If it persists, update both OxygenOS (Settings > About device > Up to date / Software update) and WhatsApp, since older system builds had notification-handling bugs. See how others solved this on Reddit