VB6 can't talk to C# DLL

Hi All,
I have a C# DLL which was written for me to interface with my VB6 program.  The DLL is COM-Visible and the Register for COM interop selected.  The DLL has 3 methods Initialization, Up and Dn.

I have a small VB6 test program which access the DLL.

I'm using VS 2017 (run as administrator) to build the DLL
I have Visual Studio (VB6) on the same machine - A Windows 10 PRO system.

In my VB program I have a reference to the DLL (actually the TLB).  Intellesense works fine - I can see all three methods.
My startup code is:

Public Sub Main()
    Dim AM as AudioManager
    Set AM = New AudioManager       ' <<<==== Error here
  
End Sub

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When I run the program I get an error at the Set statement - Runtime 429 - "ActiveX component can't create object".
I've done quite a bit of research on the web about this, and most of the similar issues are when someone tries to move a project from a development environment.  In my case , I'm getting this on the development system.
I have tried:
So far nothing seems to work.  I have put the DLL and TLB into the System32, SYSWOW64 and my VB6 application folders (registering it in each after removing from the previous location) - doesn't help.
Anyone have any ideas?
Thanks in advance