WhatsApp for Redmi 9

This is the proximity sensor staying triggered after a call, a common MIUI quirk on the Redmi 9 series. Test the sensor by opening the dialer and entering *#*#6484#*#* (or *#*#64663#*#*) to reach the hardware test menu, then run the proximity sensor check; if it reads incorrectly, clean the top bezel and remove any screen protector covering the sensor. If it still misbehaves, force-stop WhatsApp in Settings > Apps > Manage apps > WhatsApp, clear the app cache, and reboot. See how others solved this on Reddit

On the Redmi 9 this usually happens because the proximity sensor thinks the phone is at your ear, so playback routes to the quiet earpiece instead of the loudspeaker. Make sure nothing covers the top of the screen and that you tap Play with the phone flat on a table, not near your face. If it persists, clear WhatsApp's cache in Settings > Apps > Manage apps > WhatsApp > Clear data > Clear cache, and turn media volume up with the side keys while a voice note is actually playing. See how others solved this on Reddit

MIUI updates often re-apply aggressive battery rules that kill background apps. Go to Settings > Apps > Manage apps > WhatsApp > Battery saver and set it to No restrictions, then back in App info enable Autostart. Also open the Security app > Permissions > Autostart and toggle WhatsApp on, then reboot so the changes take effect. See how others solved this on Reddit

MIUI's battery optimization suspends WhatsApp in the background, which drops the Web session. Set WhatsApp to No restrictions under Settings > Apps > Manage apps > WhatsApp > Battery saver, and lock WhatsApp in the Recents screen by pulling its card down and tapping the lock icon so MIUI won't clear it. Keeping the phone on Wi-Fi and turning off battery saver mode also helps the link stay alive. See how others solved this on Reddit

This is MIUI killing WhatsApp in the background, the most common Redmi 9 notification issue. Enable Autostart for WhatsApp (Security app > Autostart), set Battery saver to No restrictions in Settings > Apps > Manage apps > WhatsApp, and confirm notifications are allowed under that same app's Notifications section. Finally, turn off background-activity restrictions under Settings > Battery > Battery saver. See how others solved this on Reddit

MIUI is delivering the call audio but blocking the full-screen notification. In Settings > Apps > Manage apps > WhatsApp > Notifications, open the Calls category and enable it with Floating notifications and lock-screen display turned on. Also grant WhatsApp the Display pop-up windows while running in background permission under its Other permissions, and turn Autostart on so incoming calls show properly. See how others solved this on Reddit