How to get running/existing BricscadApp.AcadApplication instance C#

Hi all,
I'm brand new in Bricscad world.
I'd like to implement an external .NET client integration for this CAD.

I've an application console which refers a class library that provides the following class method:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


//using AcRx = Teigha.Runtime;
//using AcDb = Teigha.DatabaseServices;
//using AcAp = Bricscad.ApplicationServices;
//using AcEd = Bricscad.EditorInput;
//using AcGe = Teigha.Geometry;
//using AcWn = Bricscad.Windows;
// com
using BricscadDb;
using BricscadApp;
using System.Runtime.InteropServices;
using Bricscad.ApplicationServices;
using Microsoft.Win32;
using System.IO;
using System.Diagnostics;
using System.Threading;


public class BricscadProvider : IDisposable
  {
    private string ProgID = "BricscadApp.AcadApplication.21.0"; //"BricscadApp.AcadApplication";
    BricscadApp.AcadApplication BrApp = null;
    BricscadApp.AcadDocument BrDoc;

    public BricscadProvider()
    {
      BrApp = GetRunningApp();
      if (BrApp == null)
        BrApp = StartApp();
    }

    internal AcadApplication GetRunningApp()
    {
       try
       {
               var app = (AcadApplication)Marshal.GetActiveObject(ProgID);
               return app;
       }
       catch (System.Runtime.InteropServices.COMException exc)
       {
          int codeError = exc.ErrorCode;
          return null;
       }
    }
... // rest of class code
} // end of class

My problem is that, even though I have a running Bricscad instance (in TaskManager/Details I can clearly see it!!!), GetRunningApp() method throws a COMException with -2147221021 error code value and returns null value.

I'm reading several questions on this forum and the 'CsBrxMgd' project's code [this is the sample project provided by Bricscad within its software installation directory] and code examples use two call options:
1. (AcadApplication)Marshal.GetActiveObject(ProgID);
2. AcAp.Application.AcadApplication as AcadApplication;

Unfortunately, both throw the COMException.

How to retrieve the running instance? Any hint?
T&R,
LemonXXX