Struggling to access very old DLL

We have a very old DLL that is no longer supported by a vendor, that we need to try and get working via a new piece of software as part of transitioning away from it. It was written in 2000 (!) and we have a fair bit of documentation for it, telling us that it is an ActiveX iSAEDataObject component and has a number of services within it.

I've googled just about everything I can think of on the topic, and have seen there is a lot of references to making sure it is set to build as x86 (I have); I'm just trying to run it in the simplest of VB console applications to try and interact with it.

It registered successfully using regsvr32, and I can import it as a reference into my solution. From there, there are 5 classes, but two have methods showing underneath them in Object browser, and the other three don't - only New().

But... even if I select one that does have a method and try to run it, it gives me this error:

System.Runtime.InteropServices.COMException: 'Retrieving the COM class factory for component with CLSID {FDF93D0E-1D17-11D4-8F41-00C04F566282} failed due to the following error: 800a801d Exception from HRESULT: 0x800A801D.'

I'm desperate to get this going, and have googled and googled; but can't seem to find much else other than the 32 vs 64 bit info. Any help would be gratefully accepted :)

Have been working on it all day today, and have got a little further. In the Object Explorer within Excel, I can see the methods - so hopefully inching forward; I just need to understand why I can't see them from within the iDE.

I also got rid of an error by downloading and registering MSRDO20.dll; so now am only left with (no doubt the most important!):

Could not determine the dependencies of the COM reference "iSAEDataObject". Error loading type library/DLL. (Exception from HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY))