Type.gettypefromprogid not returning the correct type name

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C#

I’m trying to access a method from another assembly using Activator.CreateInstance method. This works fine in a test application but fails when I implement the same logic on the enterprise application.
The structure of the projects goes like this

namespace SampleInterface // Class Library
{
    public interface IMethodExec
    {
        void TestMethod();
    }
}

namespace ProjectB // Class Library configured for COM+
{
    public class ClassB : IMethodExec
    {
        public void TestMethod()
        {
            //business logic goes here – uses external dll
        }

    }
}

namespace ProjectA // Windows application
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            IMethodExec exec = null;
            Type type = Type.GetTypeFromProgID("ProjectB.ClassB");
            exec = Activator.CreateInstance(type) as IMethodExec;
            exec.TestMethod();
        }
    }
}

namespace EntApp //Class Library configured for COM+
{
    public class Exec
    {
        IMethodExec exec = null;
        Type type = Type.GetTypeFromProgID("ProjectB.ClassB");
        exec = Activator.CreateInstance(type) as IMethodExec;
        exec.TestMethod();
    }
}

When I run ProjectA, it works correctly and Type type is
Name = "ClassB" FullName = " ProjectB.ClassB” at run-time

When I call ProjectB from EntApp, it fails at Activator.CreateInstance as Type type is Name = "__ComObject" FullName = "System.__ComObject" at run-time. EntApp is called from a client application. Any solution will be greatly appreciated. I’m open for alternative solution as long as the changes are in ProjectB and SampleInterface and method calling approach from EntApp.

What I have tried:

Tried referencing the ProjectB directly but the references in ProjectB were a conflict with the references in EntApp