Open settings-apps-and select app you want-then you should see under autostart will be one more check box named popup, enable it to get on screen draw apps working...
It caused me headache for few days but now that i understand it seems xiaomi has lots of good network , premission and other features to try to protect privacy etc.
One day i put all on ask in premissions and one simple app tahat counts pushups with proximity sensor wanted contact list , location , imei etc..
Also allows to disable ads by blocking internet access...
Pre installed soft is quite good on muiui rom