If System Preferences doesn't accept a valid administrator password when you click the lock to make changes, try these solutions.
Your Mac asks you to enter the name and password of an admin account when it needs to verify that you have permission to make changes. For example, you must authenticate as an administrator when you click the lock in System Preferences, enter certain commands in Terminal, or set a firmware password.
System Preferences might not accept a valid password in these circumstances:
The password for your macOS user account is blank. If you have been using a blank password to log in to your Mac, change your password in Users & Groups preferences. Don't use a blank password.
While using macOS Big Sur 11.1, your Mac with Apple T2 Security Chip has an issue that requires resetting the SMC. System Preferences should accept your password after you reset the SMC.
