Please login as root to reset the number of unsuccessful log-in attempts for the admin account, which enables the account if it has been locked out.
Use the following command to see the status of the account:
# scm tally status <username>
Sample command output for resetting the user account for admin:
[[email protected] ~]# pam_tally2 -r -u admin
Login Failures Latest failure From
The default of three maximum login attempts can be changed by going to the Settings > Security in the GUI.