Can I uninstall security updates for rooting?
What Updates did you previously install ?
What Android Version are you on ?
What Device are you using ?   

Samsung has a feature called Knox that is literally the fort knox of Androids, Root abilities on Samsung device's are rare.  

For your device, someone may have a specific method of unlocking the bootloader or even using ODIN to flash a pre-rooted firmware.  

For a successful root, it mainly comes down to...


Android Version
Device Lock Status
CPU Model
OTA Updates installed


Each area can stop you from getting a successful root.

The usual method for Samsung device's is to use Odin and flash a custom recovery, then from that you would install SuperSU or Magisk.zip files.  

I need more information to help you any further.


  Notes :
     Samsung devices will not allow you to use some feature's on a rooted device... It is why many Samsung owners end up using custom firmware like Lineage ( A.k.a CyanogenMod )