The .NET Framework version 3.5 is not installed by default in Windows® 8, Windows® 8.1 or Windows® 10. The eNICQ 5 application requires the .NET Framework version 3.5 specifically. Having a later version of the .NET framework (such as 4.5, etc.) is not sufficient to meet eNICQ 5 system requirements.
For information on how to properly install the .NET framework 3.5 on these versions of Windows, please see the following MSDN article: