looks like phone must be rooted!somewhy software can't root the phone automatically, maybe i have to root your device manually?
here`s quick unlock guide:
to root phone manually you have to:
Operation: Reset FRP/React/EESelected model: SM-G935FSoftware version: 26.1Checking local file... not foundSearching server... OKDownloading file... OKChecking local file... OKSearching USB Flash Interface... detected COM42Setup connection... OKReading data from phone... OKSending data to phone... OKWaiting ADB device... OKReading phone info...Model: SM-G935FAndroid version: 6.0.1Product code: SM-G935FZDAMTZPhone version: G935FXXU1APEQPDA version: G935FXXU1APF2CSC version: G935FOJV1APF1CSC country code: ZambiaCSC sales code: MTZHW version: MP 0.801Phone S/N: RF8H22GQ49RModem board: SHANNON335RF cal date: 20160228IMEI: Checking Super user right... trueErasing FRP... OKRestore original kernel? YesChecking local file... not foundSearching server... OKDownloading file... OKChecking local file... OKRestoring kernel... OKRebooting phone... OKReset FRP doneDone with Samsung Tool PRO v.26.1