WhatsApp for Asus Zenfone 8 Flip

ZenUI's aggressive battery management is the usual cause. Go to Settings > Apps > WhatsApp > Battery and set it to No restrictions (don't optimize). Then open the Mobile Manager (PowerMaster) app and remove WhatsApp from any auto-start or sleeping-app restrictions so it can sync in the background. Allowing Wi-Fi to stay on during sleep under Settings > Network & internet > Internet > Wi-Fi preferences also prevents batched, late-arriving alerts. See how others solved this on Reddit

First confirm WhatsApp's notifications are allowed under Settings > Apps > WhatsApp > Notifications, and that inside WhatsApp under Settings > Notifications the message and group toggles are on. The bigger fix on ZenUI is whitelisting the app: set Settings > Apps > WhatsApp > Battery to No restrictions and enable its auto-start in the Mobile Manager (PowerMaster). Also check that a Do Not Disturb schedule isn't silently muting it under Settings > Notifications > Do Not Disturb. See how others solved this on Reddit

Inconsistent delivery is usually background restrictions kicking in when the battery saver engages, so set Settings > Apps > WhatsApp > Battery to No restrictions and turn off any adaptive battery feature under Settings > Battery. Lock WhatsApp in the recent-apps view (tap the app icon at the top of its card and choose Lock) so ZenUI won't close it during memory cleanup. As a last step, toggle notifications off and back on inside WhatsApp > Settings > Notifications to rebuild the channel. See how others solved this on Reddit

Make sure WhatsApp can display over the lock screen. Go to Settings > Apps > WhatsApp > Notifications, open the Calls category and enable it along with Pop on screen. Then grant Settings > Apps > Special app access > Display over other apps > WhatsApp so the full-screen call UI can appear. If calls still ring silently in the background, remove WhatsApp from battery optimization via Settings > Apps > WhatsApp > Battery > No restrictions. See how others solved this on Reddit

Custom per-chat notifications only work if WhatsApp's notifications are fully enabled at the system level first, so check Settings > Apps > WhatsApp > Notifications and turn on the Messages and Group message categories. Inside the chat, tap the contact name > Custom notifications, tick Use custom notifications, then set the tone and pop-up. If it reverts, confirm Do Not Disturb isn't active, then clear and re-apply the override. Restarting WhatsApp afterward helps the custom setting save reliably. See how others solved this on Reddit

This is the ambient wake-on-notification behavior. Turn it off under Settings > Display > Lock screen by disabling the option that wakes the screen for new notifications (sometimes labeled Ambient display or New notifications). If you'd rather keep it for other apps, instead set WhatsApp's notifications to Silent under Settings > Apps > WhatsApp > Notifications, which stops them from lighting the display. See how others solved this on Reddit