If none of the administrators can log to the Management Client because of account-related issues, you can create an emergency administrator account. 
Steps
- 
On the command line of the Management Server computer, stop the Management Server service. 
- 
 Create an account with unrestricted permissions (superuser) using the sgCreateAdmin script (located in the <installation directory>/bin folder). 
    Note: If you installed the Management Server in the C:\Program Files\Forcepoint\SMC directory in Windows, some program data might be stored in the
                    C:\ProgramData\Forcepoint\SMC directory.  
 
Result
 You can now log on to the Management Client using this account, change passwords, and create new accounts normally.