Password works except to log in

I get into my admin account via autologin and my password gets me into Accounts, Security, Parental Controls, etc., but none of the password changes I make work at the login screen.

No passwords work at the login screen. Neither my admin password, nor the managed account password, nor the master password works at login screen.

I noticed the problem when I set up a managed account for my daughter. (Very thankfully, I left the computer set for autologin while I made the changes.) So, my admin password seems to work everywhere except when I log out and try to log back in, and neither do any other passwords function at the log in screen. How do I fix this? I would like to have multiple accounts on my computer and be able to password protect my admin account (in a way that allows me to access it).