I don't get that prompt. I'll tell you exactly what I do and what happens:
1) Download Multiwindow Toggle
2) Download Data Toggle APK
3) Click Data Toggle APK. Screen shows up asking if I want to update the app. There are two buttons at the bottom: "Install" and "Cancel"
4) Press Install
5) Error message comes up saying the app cannot be installed
There is no way I am the only person with this problem. I got this S6 from an AT&T store, it's not like it's a bootleg. Someone please help
Under" lock screen and security" we have an option "unknown sources". Please make sure that is enabled before you install the apk.
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BlackBerry > Lumia 710 > S3 > Nexus 4 > Note 2 > S6 Edge