I can't seem to turn off or change my lock screen pattern in the Galaxy S8plus.
I presume you are going to the proper place in Settings to Enter a Pin or Pattern, maybe Face, or Fingerprint lock. I don't know the S8+.
Assuming you are, it sounds like a "flakey" possibly occurring after a software OTA update. Did you get one recently?
I recommend first, try a System Cache Wipe. This is not done from settings, but from the recovery menu. I don't think VZW has the steps on their site. Google it. You'll find it.
If that doesn't help, I'd backup my important content onto a PC, then I'd perform a Factory Device Reset (FDR).
If you use Samsung Pay or Android Pay, you can't turn off the lock screen completely until you remove the applications that require additional security.
