On Windows XP and Windows Server 2003, the Security Agent shows the offline status and gives the same status right after installation.
The WFBS Security Server uses SHA2 256 or higher encryption to verify if the agent can connect to the security server. This problem happens because there is an issue with the usage of this encryption method (SHA2 256 or higher) on Windows XP and Windows Server 2003.
Microsoft has ended the support for Windows XP and Windows Server 2003 and this change affected software updates and security options.
To fix the issue, install Microsoft hot fix 968730. For instructions, refer to this Microsoft article: Windows Server 2003 and Windows XP clients cannot obtain certificates from a Windows Server 2008-based certification authority (CA) if the CA is configured to use SHA2 256 or higher encryption.
Installing the hot fix allows the system to obtain certificates from a Windows Server 2008-based certification authority (CA) through SHA2 256 or higher encryption.
If the security agent still shows offline, please contact Trend Micro Technical Support.