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if you dont have root showing up after a dirty flash try installing the SuperSU app from the play store it seems that the binary is there but the app is not.

if installing the app doesnt work you can flash one of these zips to force system root http://forum.xda-developers.com/apps/supersu/v2-64-2-66-supersu-mode-t3286120
sorry about this guys i knew updating from the 2.52 root would cause issues :( but it was kinda forced on us with the recent play store updates for SuperSU