samsung - How to Install system app with SE Linux enforced on Galaxy s7 Android 6.0.1

first, sorry for my english :)

i try to install a user app (installed in /data/app/) as system app on my new galaxy s7 : - Android 6.0.1 - Rooted - factory ROM

I follow many tutorials :

http://www.addictivetips.com/mobile/how-to-install-any-app-as-system-app-on-android/ http://www.androidauthority.com/install-user-app-as-system-app-how-to-93522/

After reboot, my application is in the the folder /system/app but i can't launch it: it crash when i launch apk directly, even if permission are correctly set.

With another smartphone (samsung s4 rooted with cyanogenmod and SE Permisive), the copy paste technique work well.

Someone knows why i can't launch it ?

Thanks a lot