First, I hit the same mine:

"... Failed to instantiate .Net object [Unwrapped, QI for IDispatch] [0x80004002] No such interface supported ..."

In order to load the assembly and class in it successfully, I had to change my AssemblyInfo.cs file regarding the visibility of the types in it.

// some code above

// This sets the default COM visibility of types in the assembly to invisible.
// If you need to expose a type to COM, use [ComVisible(true)] on that type.
[assembly: ComVisible(true)]

// some code below