Fix: Agent Showing "Offline" / Not Connecting
Edit ArticleStep-by-step resolution when an endpoint is installed but does not appear online in the console.
Sentinel Operations Team
5 min read
Updated August 28, 2026
v3.2Diagnosed Problem
Endpoint appears as "Offline" or "Last Seen > 10m ago" in the Sentinel Web Console, even though the computer is turned on and connected to Wi-Fi/Ethernet.
Visible Symptoms
- Console badge is grey (Offline).
- Agent log contains: "Heartbeat failed: connection timed out".
- Local events are queuing up in SQLite database.
Possible Root Causes
- Server base_url in sentinel-agent.toml has a typo or wrong protocol (e.g. http:// instead of https://).
- Corporate firewall or guest Wi-Fi blocks outbound Port 443.
- DNS cannot resolve your Sentinel server hostname.
- Windows system clock is skewed by > 15 minutes, causing TLS handshake failure.
Step-by-Step Resolution Procedure
1Check sentinel-agent.toml Base URL
Confirm the server base_url in config matches your production domain exactly.
powershell
1Get-Content "C:\Program Files\Sentinel\config\sentinel-agent.toml" | Select-String "base_url"
2Test Port 443 Outbound Connection
Verify client endpoint can reach server on port 443.
powershell
1Test-NetConnection -ComputerName "endpoint.yourcompany.com" -Port 443
3Synchronize System Clock
Ensure Windows time is accurate to prevent TLS cert errors.
powershell
1w32tm /resync /force
4Restart Sentinel Service
Restart the agent to force an immediate heartbeat attempt.
powershell
1Restart-Service SentinelAgent
How to Verify the Fix:Check the Sentinel Console. Within 15 seconds, the endpoint status should switch to Green "Online (Just now)".
Technician Verification Command:
powershell
1Get-Content "C:\ProgramData\Sentinel\logs\$(Get-Date -Format yyyy-MM-dd).log" -Tail 20
Tags:#Offline#Heartbeat#AGENT-1001#Connection
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