Siebel Error: SBL-SSM-00004: SISNAPI Hello failed. The server component could be down.

This error message suggests there is a failure communicating the siebel server component.
The request to connect to the said component can be either from a user request (or) another component (or) external application.

The reasons for this error could be any of the below:

1. The Siebel server is down.
2. The component is not enable, running (or) available on this server.
3. If the server and the component are both running, then the connection information to connect to the component might be incorrect.
4. Network connectivity issues.

If none of these help, then look for any accompanying error messages in the logs which could lead to the failure.

Troubleshooting steps:

1. Verify the Siebel server and the component are enabled and Running.
2. Verify the connectivity information (ConnectString) to this component in the eapps.cfg file.
3. Verify if all Siebel SWSE, Gateway server, Siebel servers and the database can communicate.