https://youtu.be/F7mkv0_aRpg Well, you won't even know this till you want to watch an interesting movie on Netflix app or Stream on DSTV Now app. There are lots of app that will only work well if your device is certified of Google play store.
To check whether your device is certified or not, open Google play store app, tap on the three menu bar at the top left, click on settings and scroll down to the last submenu option.

There are many reasons why this happens and if it has happened to your Android device, then this is a permanent fix.
[YOUTUBE]
https://www.youtube.com/watch?v=F7mkv0_aRpg [/YOUTUBE]
note: requires root.