Symantec Endpoint Protection Manager (SEPM) is experiencing communication issues and the Endpoint Protection (SEP) clients are showing as offline. A HTTP 404 error has been identified in the logs.
Step 1: Follow the Disaster Recovery steps to backup the necessary information for your SEPM. For details read this article: Best Practices for Disaster Recovery with the Symantec Endpoint Protection Manager
Step 2: Reinstall IIS:
In the this step you will need the Operating System disk for you SEPM server.
For IIS 6.x please follow the instructions in this Microsoft KB to reinstall IIS: How to remove and reinstall IIS 5.0, 5.1 and 6.0
Step 3: Run a repair of the SEPM:
Open the Control Panel,
In Windows XP/2000/2003 open Add or Remove Programs by clicking the Start button > Settings > Control Panel, and then clicking Add or Remove Programs.
Click on the Symantec Endpoint Protection Manager in the list of programs. Click on Change, click on Repair and follow the prompts to the end.
In Windows Vista/Windows 7/Windows 2008 open Programs and Features by clicking the Start button > Control Panel > Programs, and then clicking Programs and Features. Click on the Symantec Endpoint Protection Manager in the list of programs. Click on Repair and follow the prompts to the end.
Step 4: Run the Management Server Configuration Wizard:
Go to Start > Programs > Symantec > Symantec Endpoint Protection Manager > Management Server Configuration Wizard.
And run the management configuration wizard to reconfigure the SEPM with the existing database as per the wizard prompts.
The end result should be the IIS configuration is restored to its original state and the SEPM can now communicate with a HTTP 404 error.
If the issue is not resolved following these steps you may need to do a complete reinstall of the SEPM following the article previously mentioned Best Practices for Disaster Recovery with the Symantec Endpoint Protection Manager