The Xiaomi Mi Mix is a brilliant device, but not everything can be perfect. Xiaomi introduced the Mi Mix, which boasts a revolutionary design that maximizes screen real estate much to the delight of consumers. Although a rebel when it comes to design, the Mi Mix seems to have a few more things to work on, such as the MIUI's aggressive battery optimization set-up killing push notifications.
In an article by Ben Sin from Forbes, it seems that a solution for the push notification problem has been found. He mentions that he has received half a dozen emails and tweets inquiring about how he was able to solve the push notification issue. He first decided to reply to every query one by one, until he came to realize that it would be much more feasible to write a quick guide on Forbes instead.
Here are the steps that Ben took to fix the push notification issues. These steps are for the Xiaomi Mi Mix and the Xiaomi Mi Note 2, which run Xiaomi's latest software, MIUI 8. However, he notes that he is unsure whether all of the steps are needed. As he has tried every step, only until adding step 5 was he able to fix the problem.
Step 1. Go to settings, then manage apps then battery usage, then choose apps. Within the option, choose all the apps you want to receive push notifications and select "No restrictions."
Step 2. Go to settings, then permissions, then autostart. Here, you can choose pick the apps you want to receive notifications, and toggle the switch to activate it.
Step 3. Go to settings, next choose app notifications, after which pick the apps you want to receive notifications, then turn the toggle for "Priority" on.
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," which is the square button on stock Android, or the button with three horizontal lines on the Xiaomi Mi Mix. Afterwards, find the app you want to receive push notifications for, pull down on it to "lock it", so it never gets cleared.
Step 5. Requires Developer Options privileges, which can be enabled by going to settings then choosing About Phone. Tap on the MIUI version tab eight times. This should result in you receiving a message that reads "you are now a developer." Afterwards, move out of settings, then go to developer option. Scroll to nearly the end and look for "memory optimization," and turn it off.