Azure Service Bus - Unauthorized access. 'Send' claim(s) are required to perform this operation

I am trying to access `Azure Service Bus` `Queue` from my `Windows Service` application.
I am following [this](https://github.com/Azure/azure-service-bus/blob/master/samples/DotNet/Microsoft.ServiceBus.Messaging/RoleBasedAccessControl/Program.cs) sample.

I want to protect this `Azure Service Bus` using `Azure Service Principal`  Below are the steps I have implemented

 1. Register an application named `pc-shutdown-producer` in `Azure Ad`
    representing my `Windows Service`
 2. I have created my Azure `service bus namespace` named `shutdowncomputer` 
 3. Inside `Access control (IAM)`, I have added `Role Assignment` with below values
       - Role - `Azure Service Bus Data Owner`
       - Assign access to - `pc-shutdown-producer`

As per my knowledge above configuration will let `pc-shutdown-producer` application to manage all the resources in the servicebus namespace.
 4. Apart from this, I have also provided `pc-shutdown-producer` delegated API Permissions to access the service bus namespace.

Below is my C# code.

 public async Task Init()
    		{
    			string authority = $"https://login.windows.net/{TenantId}";
    			ITokenProvider tokenProvider = TokenProvider.CreateAzureActiveDirectoryTokenProvider(AuthenticationCallback, authority);
    			var endpoint = new Uri($"sb://shutdowncomputer.servicebus.windows.net/");
    			var entityPath = "shutdownrequest";
    			var qc = new QueueClient(endpoint.ToString(), entityPath, tokenProvider);
    			Message m = new Message();
    			m.Body = Encoding.ASCII.GetBytes("{id: 1, name: 'hemant'}");
    			m.ContentType = "application/json";
    			try
    			{
    				await qc.SendAsync(m);
    			}
    			catch (Exception ex)
    			{
    				//I am getting exception here. 
    				//Unauthorized access. 'Send' claim(s) are required to perform this operation.
    				throw ex;
    			}
    		}
    		private async Task<string> AuthenticationCallback(string audience, string authority, object state)
    		{
    			string accessToken = string.Empty;
    			IConfidentialClientApplication app = ConfidentialClientApplicationBuilder.Create(AppId)
    				.WithAuthority(authority)
    				.WithClientSecret(Password)
    				.Build();
    			var serviceBusAudience = new Uri("https://servicebus.azure.net");
    			List<string> claims = new List<string>();
    			claims.Add($"{serviceBusAudience}/.default");
    			try
    			{
    				var result = await app.AcquireTokenForClient(claims.ToArray()).ExecuteAsync();
    				accessToken = result.AccessToken;
    			}
    			catch (Exception ex)
    			{
    				//No issue here.
    				Console.WriteLine(ex.Message);
    			}
    			//Successfully able to retrieve a token.
    			return accessToken ;
    		}

Upon executing `Init()` , I am getting below exception message.

`Unauthorized access. 'Send' claim(s) are required to perform this operation. Resource: 'sb://shutdowncomputer.servicebus.windows.net/shutdownrequest'. TrackingId:52c0eedcf19d4513a8ec105943859764_G12, SystemTracker:gateway7, Timestamp:2020-05-11T06:59:01`

Thanks

Regards, Hemant Shelar