This cannot work, adding a reference to a .tlb file causes Visual Studio to use a <COMReference>
element in your project file that states the type library {guid}. Not the file. You'll inevitably get the registered Win7 version of the type library, not the Win8 version. So you'll see the Win8 additions missing. This is a Good Thing, it ensures your program can actually be debugged and tested.
You must instead run Tlbimp.exe on the Win8 machine to convert the type library to an interop library. You'll get MbnApi.dll, copy it to your Win7 machine into your project directory and add a reference to it.