Symantec Endpoint Protection Manager Admin Account got locked after too many logon attempts.
Symantec Endpoint Protection Manager locks out an administrator for a certain length of time after a number of unsuccessful logon attempts. By default, the management server locks out an administrator for 15 minutes after five failed attempts.
You cannot unlock the administrator account without waiting for the specified period of time to pass.
More information is now located at techdocs.broadcom.com: