AtlReportError not returning error string from c++ COM dll in c# application

We have upgraded an old VB6 app to .NET C# and use en existing C++ COM dll.  Now in the VB6 app, when the C++ COM dll threw an exception with AtlReportError, the error string was picked up in the VB6 app and shown to the user providing them with a detailed error message.

Now using the exact same C++ COM dll in C# when the C++ COM dll throws an exception, we simply get back Exception from HRESULT: with no error message string.  The innerexception is also null.

We would prefer to not have to port the dll to managed C++ or do any re-writing of it since it is rather large and contains a fair amount of process logic.

The COM dll functions all work and the reference was added to the .NET project through the references dialog.  Is there some other setting I am missing or does AtlReportError not play nice with .NET COM interop?