Intune Graph success: 403 (Forbidden) - Visual Studio

Please excuse my ignorance in Visual Studio coding. I am simply trying to follow the example in 

https://docs.microsoft.com/en-us/mem/intune/developer/intune-graph-apis

I followed all the steps mentioned, set the required API permission and consent for the App, copied and pasted the code, and edited it with the App ID. When I run the project, I get the request for credentials popup Window then followed by the the error message "System.Net.Http.HttpRequestException: 'Response status code does not indicate success: 403 (Forbidden).'"

Can you please assist?