How to fix the push notifications on Xiaomi MIUI 8:
Xiaomi MIUI 8 phones are using very aggressive battery saving methods. These proprietary features may cause the 2N® Mobile Video application (and other communicators and instant messaging apps) unreachable when running in the background.
Proceed please with following steps:
- Go to settings --> manage apps' battery usage --> choose apps. From there, pick all the apps you want to receive push notifications and select "No restrictions."
- Go to settings --> permissions --> autostart. From there, pick the apps you want to receive notifications, and toggle the switch to turn it on.
- Go to settings --> app notifications --> pick the apps you want to receive notifications, then turn the toggle for "Priority" on.
- Lock the app in the "recent apps"/ "app overview" plane. Do so by first opening the apps, then press the "recent apps/overview button" (that's the square button on stock Android, or the button with three horizontal lines on the Mi Mix). From there, find the app you want to receive notifications, pull down on it to "lock it", so it never gets cleared.
- This last step requires Developer Options privileges. To enable that, go to settings --> about phone and tap on MIUI version tab like eight times. You should then get a little message saying "you are now a developer." Then head back out to settings, go to developer option, scroll to nearly the bottom, find "memory optimization," and turn it off.
For further details see this article: https://www.forbes.com/sites/bensin/2016/11/17/how-to-fix-push-notifications-on-xiaomis-miui-8-for-real/#2b07d4bb7572