After flashing root fileand finish and boot after restart.
go to google play and update supersu then run it and update it normally .
after it being updated it will try to disable Knox.
it will take long time.. just reboot your device and run supersu and itwill ask you to disable Knox. chose OK. and done.
proof in attachment.
Thank you post's owner and this comment is also very helpful. My Note 2 is rooted. :good::good:
BR
Eagle18