Without knowing more details, I'm going to assume one of two things happened.
1) You downloaded the CF-Auto-Root file for the SM-G920F—which is listed for Android Version 6.0.1, which is not what you have. Device bricked.
2) You had a locked bootloader, which is meant to prevent flashing custom firmwares. Device bricked.
Am unfamiliar with 6.0.1+ rooting and what's changed since 5.1.1 since my own devices haven't gotten the update. You'll probably want to head over to the CF-Auto-Root thread on xda-developers and see if anybody, possibly Chainfire himself, can offer any advice.