Windows Media Foundation -- IMFActivate::ActivateObject() RPC Error?

I've had this problem for a few days now. I would like to interface with a web cam using Windows Media Foundation classes, but for whatever reason, any time I call

IMFActivate::ActivateObject()

To open up a capture source, it yields a 0x800706d9 Error:

0x800706d9 : There are no more endpoints available from the endpoint mapper. HRESULT

I am using Windows 10 LTSB, and have used 2 different machines with different web cams, all yielding the same result. I have even used an off-the-shelf library from here (https://www.codeproject.com/Tips/559437/Capturing-Video-from-Web-camera-on-Windows-and-by) that is supposed to work, but I get the same problem at the same function.

Here is the particular line in that library:

hr = pActivate->ActivateObject(
        __uuidof(IMFMediaSource),
        (void**)&pSource
        );

It is a cryptic problem that I can't seem to solve. Has anyone dealt with this before?

Thanks