Hello , my device has its latest firmware , Android Marshmallow , but i noticed that when i download an official apk (free) ,

manually install it , it always says it cannot install or App not installed , but Unknown sources is already turned on in my device ,

any help or guide on how to fix this? (Note: my device is Rooted , using the instruction i saw here , but i think its not because of that.)





Thanks,

NicoTing