Notification Settings on MIUI (Xiaomi)
Before referring to the following instructions, please read the general notifications settings article.
Step 1: Go to Settings > Manage Apps’ Battery Usage > Choose Apps. From there, pick all the apps you want to receive push notifications for and select “No restrictions”.
Step 2: Go to Settings > Permissions > Autostart. From there, pick the apps you want to receive notifications for and toggle the switch to turn it on.
Step 3: Go to Settings > App Notifications and pick the apps you want to receive notifications for, then toggle the Priority switch.
Step 4: Lock the app in the Recent Apps/ App Overview plane. Do so by first opening the apps, then press the Recent Apps/ Overview button (the square button on stock Android or the button with three horizontal lines on the Mi Mix, or swipe up and hold if you’re on MIUI 10). From there, find the app you want to receive notifications for and pull down on it to “lock” it so it never gets cleared.
Step 5: This last step requires Developer Options privileges. To enable these, go to Settings > About Phone. Tap on the MIUI version tab multiple times. You should then receive a little message saying “You are now a developer”. Then head back to Settings, go to Developer Options, scroll to near the bottom, find Memory Optimization and turn it off.