I am using a Mi4i. I can't download apps from the Play Store when the SIM is in roaming. How can I do this?
This is one of the problem in Android Nougat and wasn't solved in the subsequent updates. This problem leaves you with, only way of downloading the app is to download it's apk file from other sources through your browser while you are on mobile data otherwise apps are getting downloaded when you connect your phone through wifi.
To follow updates on this you can go here https://productforums.google.com/forum/#!topic/nexus/21wGieItCik