[Samsung Galaxy S7 Edge Questions and Answers] shah22:
Maybe you are using an older bootloader ? Can't say for sure whats causing it, the method you used above I think required system modifications, but you are using a march 2017 stock rom, so it looks updato don't has V2 bootloader firmwares for DBT, problems may happen when flashing an older bootloader on a newer one, it could also be your pc or other hardware problem, but in case try again and download samfirm from here : https://xdaforums.com/attachment.php?attachmentid=3803841

Enter DBT as your region and model SM-G935F , it will download the latest stock available, be sure option for auto decrypt, check crc32 and binary nature are ticked.

After that check oem unlock and usb debugging is enabled and follow the steps :

1. Put phone in download mode, use original usb cable, and make sure pc usb port is working correctly. Also phone must be charged above 50%.

2. Download odin 3.13.1 from here https://xdaforums.com/attachment.php?attachmentid=4431597&d=1519662712

Latest twrp available https://eu.dl.twrp.me/hero2lte/twrp-3.2.1-1-hero2lte.img.tar.html

Latest no verity opt encrypt https://build.nethunter.com/android-tools/no-verity-opt-encrypt/no-verity-opt-encrypt-6.0.zip

Latest stable super su https://s3-us-west-2.amazonaws.com/supersu/download/zip/SuperSU-v2.82-201705271822.zip

3. Put phone in download mode, extract the firmware downloaded above from samfirm tool and put the respective files in their boxes, use CSC and NOT HOME_CSC. Make sure no option other than F.reset time is ticked in odin options. Begin the flash procedure. After it is completed, don't reboot and place twrp zip downloaded from above in the AP tab of odin. After it is completed, stay in download mode and hold power+home+vol down to reboot from download mode and immediately switch to vol up button to boot in twrp recovery menu.

4. In twrp recovery menu, you need to swipe for system modifications or tick read only ( if you previously allowed for system modifications then you can do it again it doesn't matter, but if you previously didn't swipe for system modifications then tick read only and download systemless zip from https://xdaforums.com/s7-edge/development/samsung-systemless-devbase-encryption-t3517178 )

I will recommend this as you won't need to flash dm verity.

5. Now, go to wipe> format data in twrp recovery, after its done, flash super su and system less zip through twrp to get system less root if you don't want to get dm verity error hassle when flashing stock roms OR flash super su and no verity opt encrypt if you already have allowed system modifications. After that reboot. It may take sometime.

Also to note if you never allowed system modifications before in twrp, and you don't want to root either, then you can safely flash stock without flashing twrp or going through further steps.

This is what I could best explain according to my limited knowledge, if you still fail to flash stock in odin, then I am not sure it may be your pc or other hardware problem and you may need a repair box, try checking on another pc or some expert user to help. Good Luck.

These steps are only for installing stock rom back on previously rooted S7 edge devices using custom roms and for rooting a stock rom.. and only applies to SM-G935F