This issue has been reported so far in users with IT Security Search installed on Windows Server 2016 and it has been fixed by following this procedure:
1. Do a right-click on the "ITSearch.msi" installation file.
2. Select "Troubleshoot compatibility".
3. Let the Program Compatibility Troubleshooter detect and fix settings automatically and then click on "Test the program..."
4. After the IT Security Search installation wizard appears, follow the instructions to apply the upgrade.
5. The installation should now finish without issues.