Overview
The installer does not launch when upgrading from GFI MailEssentials version 20.3 or older to 21.1.
Resolution
Upgrade from .NET Framework version 4 to .NET Framework version 4.5.
If the issue persists make sure there are no environmental issues affecting the installation, such as antivirus or UAC (User Access Control) blocking the installation files.
For assistance, contact GFI Customer Support.