Hi I recently had to remove the lock from my samsung s8 for a repair(the charging unit had to be replaced). I am trying to enable the screen lock again but when I go to Settings->Lock screen->Screen lock type I get a message for a couple of seconds asking me to verify my identity with an option to scan your fingerprint or use your samsung account. Nothing happens when i try to scan my fingerprint except the message disappears and the Screen lock type is still none. If i try Use your Samsung Account - i enter my samsung account credentials and the message just disappears again. I have biometric security data on the phone fingerprints etc. And its the same in safe mode.
I would recommend factory resetting your device. Important: Please save any information you need prior to the factory reset because otherwise your personal information may not be recovered. If you have encrypted the microSD card, you must decrypt it before resetting the phone. Otherwise, your phone will not be able to read the data on the card. From Settings, search for and select Decrypt SD card, and then follow the on-screen prompts.
Before you perform a factory reset, be sure to back up your personal data, so you don't lose it all. Give this link a try: https://www.samsung.com/us/support/answer/ANS00062029/