Only System Admin's can unlock a user's account. In order to unlock a user's account, you need to send the user a password reset link. First click 'Users' from the Management panel on your homepage.
Navigate to the locked user and choose 'Edit User' from the Actions Menu.
On the pop-up that appears, click 'Reset Password' and a link will be generated and sent to their inbox.
In order for the account to be successfully unlocked, the user will have to reset their password. If the user does not receive the generated email, please have them reach out to firstname.lastname@example.org.