Essential Studio for Windows Forms Release Notes
Starting with version 16.2 (2018 Vol 2), you need to include a valid license key (either paid or trial key) within your applications.
Please refer to this help topic for more information
Starting with version 16.4 (2018 Vol 4), Syncfusion has removed .NET Framework 2.0, 3.5 and 4.5.1 assemblies from the Windows Forms install. These assemblies are provided in a separate add-on install.
Please refer to this help topic for more information.