Overview

You are getting "Failed to install patch scan pre-requisite" error during missing patches scan. 

Solution

The error can be caused by the Program Update issues or missing requirements for scanning operations.

1. Follow the Updating LanGuard Server Manually When Product Does Not Get Latest Definitions or Agents Do Not Update article to ensure you have the most recent Program Updates and vulnerability definitions. 
2. Ensure that the Required Settings to Scan a Machine and Successfully Install Missing Patches are in place.
3. Sometimes this error is related to using a VPN/Firewall. If you are using any of those and the issue persists after the previous steps, please disable them and rerun the scan. If it completes without any issue, you've found the root cause - address it with the help of your network administrator.

Testing

Rerun the scan. If the issue persists, please enable the debug mode, reproduce the issue (scan the machine in question), wait for 20 minutes, gather and submit the troubleshooting logs, and contact GFI LanGuard Support, describing the situation, and the name of the machine so that we can find it in the logs.