Do you have any other domain configured under Admin-->Domains.
You can search the client in the SEPM DATABASE. This is a long process but you will find out whether the client is present in the database.
Get the ComputerID and HardwareID under following key...
HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Symantec Endpoint Protection\SMC\SYLINK\SyLink
Use this SQL to get the details of the client in the MS Database
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SELECT [CLIENT_ID]
,[DOMAIN_ID]
,[GROUP_ID]
,[POLICY_MODE]
,[COMPUTER_ID]
,[HARDWARE_KEY]
FROM [sem5].[dbo].[SEM_CLIENT] where [HARDWARE_KEY] = 'put HardwareID from
above reg key'
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Then get Group name using this SQL.
SELECT [ID]
,[NAME]
,[TYPE]
,[DOMAIN_ID]
FROM [sem5].[dbo].[IDENTITY_MAP] where [ID] = 'GROUP_ID from above SQL'
Now you will be able to see to which group the client are pointing to
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REF:
https://www-secure.symantec.com/connect/forums/clients-showing-offline-even-after-reinstall#comment-3089981