If you recently installed a new version of SpreadsheetGear, you may need to remove any references to SpreadsheetGear assemblies from your project using the Solution Explorer window in Visual Studio. First, remove any old references, then, add any new ones back by using the .NET tab of the Add Reference dialog.
It is also important to note that Visual Studio 2010 replaced the MS Help 2 system with the new Microsoft Help Viewer 1.0 system. This new help system does not have Dynamic Help, though it does still support IntelliSense, and pressing F1 on a term such as "IWorkbookSet".
See SpreadsheetGear 2017 -> Getting Started -> Using Help in the SpreadsheetGear Help for more information on using the SpreadsheetGear 2017 help with Visual Studio 2005 / 2008 / 2010 / 2012 / 2013 / 2015 / 2017.
Note: It may be necessary to delete any occurences of any SpreadsheetGear assemblies from your project directory before adding any new assemblies.