License Server: Service fails to start after Windows update due to blocked port or service account change

Description
After a major Windows update or security hardening change on the license server machine, the License Server service no longer starts. The Windows Services panel may show “Starting…” then revert to “Stopped” with no clear message, or Event Viewer logs may indicate binding errors or insufficient permissions. Client machines cannot obtain licenses.

Solution

1. Check basic service status
   • Open Services (services.msc) and locate the License Server service (or equivalent name).
   • Attempt to start the service and note any immediate error messages.
   • Check Windows Event Viewer > Windows Logs > Application/System for errors related to this service.
2. Verify service account and permissions
   • Confirm whether the service is configured to run under Local System or a custom domain/service account.
   • If a domain policy change or password rotation occurred, re‑enter the correct service account credentials.
   • Ensure the account has the right to log on as a service and read the license file directory.
3. Check port binding and firewall
   • Verify the configured listening port in the license server configuration file or UI.
   • Use netstat -ano or similar tools to check if the port is already in use by another process.
   • If a conflict exists, either stop the conflicting service or change the license server port and update client configurations accordingly.
   • Confirm that the Windows firewall (or any third‑party firewall) still allows inbound traffic on the license server port.
4. Validate license file and host ID
   • Open the license file and confirm:
     • The host ID matches the current server.
     • The license has not expired and is not corrupted (no truncated lines).
   • If Windows update changed NIC ordering or adapter details, re‑check which host ID is actually used and ensure it still matches the license.
5. Restart and test
   • After resolving service account, port, and license file issues, restart the license server service.
   • On a client machine, attempt to launch a program and obtain a license:
     • If successful, document the root cause (e.g., port conflict, service account reset).
     • If not, repeat Event Viewer review for remaining errors.
     • If the problem persists, contact Support.