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Technician Diagnostics & Reference

Sentinel Agent Error Code Directory

Lookup official error codes reported in the Sentinel Management Console or client logs (C:\ProgramData\Sentinel\logs\) with verified step-by-step technician fixes.

Quick Fix for Technicians:Verify the server URL in your configuration and test outbound HTTPS connectivity using PowerShell Test-NetConnection.

Symptoms Observed:

  • Endpoint status in the Sentinel Web Console shows as "Offline" or "Last Seen > 5m ago".
  • Agent log file (C:\ProgramData\Sentinel\logs\) contains repeating errors: "HTTP connection refused: connection timed out".
  • The tray icon or diagnostics CLI reports "Heartbeat failed after 3 retry attempts".

Probable Causes:

  • The "base_url" in sentinel-agent.toml is incorrect or points to a non-existent hostname.
  • Corporate perimeter firewall or UTM device is blocking outbound HTTPS port 443 to the Sentinel server.
  • A corporate SSL-inspecting proxy is terminating the connection with an untrusted root CA certificate.
  • Local network adapter is disconnected or DNS cannot resolve the server domain name.

Step-by-Step Resolution Procedure:

1Check the Configured Server URL

Open "C:\Program Files\Sentinel\config\sentinel-agent.toml" in Notepad as Administrator. Confirm the "base_url" exactly matches your organization server address (e.g. "https://endpoint.yourcompany.com").

powershell
1Get-Content "C:\Program Files\Sentinel\config\sentinel-agent.toml"
2Test Network Connectivity & Port 443

Run a PowerShell network test to verify port 443 is reachable from the endpoint machine.

powershell
1Test-NetConnection -ComputerName "endpoint.yourcompany.com" -Port 443
3Verify DNS Resolution

Ensure the client machine can resolve the Sentinel server hostname to the correct public or internal IP.

powershell
1Resolve-DnsName "endpoint.yourcompany.com"
4Restart the Sentinel Windows Service

After fixing network or configuration issues, restart the Sentinel service to trigger an immediate reconnection.

powershell
1Restart-Service SentinelAgent
Verification Check:Check the Sentinel Console dashboard. The endpoint badge should turn Green with "Active (Just Now)". In the local log, you should see "Heartbeat acknowledged: 200 OK".