Knox is the security precaution behind Samsung now. Its just basically saying you rooted your phone. Does your phone come with a locked bootloader or are you unlocked by default? Knox will also stop you from downgrading. If you try your phone is straight dead... But you should be able to use safesteap I think.... I think safe strap is out for this one. I can see if I can find it if you would like...
Sent from my Rezound using xda-developers app. CyanogenMod 11. S-off
Verizon HTC One M8
Liquid Smooth 4.4.4 Nightlies and GPE With L S-OFF
Main MP3 Player and WiFi Device
HTC OG Droid Incredible S-OFF: Cyanogenmod 11
iPad First Gen. iOS 5.1.1 Jailbroken with GreenPois0n