WhatsApp for Redmi Note 8

MIUI's aggressive memory management is usually the cause. Go to Settings > Apps > Manage apps > WhatsApp, tap 'Battery saver' and set it to 'No restrictions', then turn on 'Autostart' so WhatsApp can run in the background. Next, open the Recents screen, swipe down on the WhatsApp card (or long-press it) and tap the padlock to lock it so MIUI doesn't kill it. If messages still won't load, clear the app cache from the same WhatsApp app page. See how others solved this on Reddit

This happens when no default PDF viewer is installed or WhatsApp can't access the file. Install a dedicated reader such as Google Drive PDF Viewer or Adobe Acrobat from the Play Store, then the first time you open a PDF, Android will ask which app to use — pick the reader and choose 'Always'. You can also set it under Settings > Apps > Default apps. Make sure WhatsApp has file access at Settings > Apps > WhatsApp > Permissions > Files and media, then re-download the PDF. See how others solved this on Reddit

First rule out a permission block: go to Settings > Apps > Manage apps > WhatsApp > Permissions > Microphone and set it to 'Allow only while using the app'. On stock MIUI, also check that the privacy 'microphone access blocked' indicator isn't toggled in quick settings. If you recently flashed a custom ROM like LineageOS, no-mic-in-some-apps is usually a missing audio policy in the build, so reflash the correct firmware/vendor image for the Redmi Note 8 (ginkgo) or try a different ROM build. See how others solved this on Reddit

Back up first: in WhatsApp go to Settings > Chats > Chat backup, sign in with a Google account and tap 'Back up' to save to Google Drive. On the new Android phone, install WhatsApp, verify the same phone number, and choose 'Restore' when prompted. To move to an iPhone, use WhatsApp's official 'Move to iOS' tool. For a manual local copy on Android, the chat databases live under Android/media/com.whatsapp/WhatsApp/Databases — copy that folder with a file manager before resetting the device. See how others solved this on Reddit

Open Settings > Apps > Manage apps > WhatsApp > Notifications and make sure 'Calls' notifications and 'Floating notifications' are enabled. Then enable 'Autostart' and, under WhatsApp's 'Other permissions', turn on 'Display pop-up windows while running in background' and 'Show on lock screen' so MIUI lets the incoming-call screen appear over the lock screen. See how others solved this on Reddit

This is MIUI battery optimization silencing background apps. Go to Settings > Apps > Manage apps > WhatsApp, set 'Battery saver' to 'No restrictions' and enable 'Autostart'. Confirm notifications are on under the same app's Notifications page with a sound selected. Turn off the global 'Battery saver' mode while testing, and lock the WhatsApp card in Recents with the padlock so the system stops closing it. See how others solved this on Reddit