When trying to update my user account password on macOS Catalina 10.15.1 in the System Preferences, under Users & Groups, with the Change Password... button, I get the error message:
Of course, I'm sure I entered my login password correctly ;-)
When my system administrator attempts to reset my password using the *Reset Password..." button in the Users & Groups system preferences, they get the error message:
What can I do to change my password?
Just a further piece of information that might be related with this issue: My account was created in a previous version of macOS and I used my iCloud password to log in and unlock my Mac. This option has been removed in recent versions of macOS. Moreover, I recently had to change my iCloud password.