Not being able to log in do you mean not being able to get into your phone? or your samsung account? If you can't get into your phone what is the error message you are receiving?
If it is your samsung account, go on line and try to login. If that doesn't work try to change your password and see if that helps.
Make sure your phone and all of your applications are up to date, check the google play store, and check the galaxy store for updates.
After all of those are up to date, go to 'settings' 'biometrics and security' and press 'secure folder' this should open up the settings for the secure foler and allow you to make changes.
Please update if this works for you.