How to Solve 'unauthorized screen' error in S9 which appears after reboot?
If you enabled “OEM unlock” in Developer options, device may be not rebooted properly. As OEM unlock setting is a function that related with device’s security, if you activated “OEM unlock” that means device protection functions and sensitive apps, including Knox and Samsung Pay will not work .
Therefore it should be deactivated. Once below screen is shown, please tap the RESET and check whether you activated “OEM unlock” option or not in Settings > Developer options.
NOTE: When you tap the “RESET” button, your all data will be erased and initialized.
After reset is done, you have to check status of ‘OEM unlock’.
But if this option is activated, you have to turn it off.
After deactivating ‘OEM unlock’ option, device will be restarted again. And then press ‘RESET’ button again