Auth0 - Unable to see/get login or signup page

I am trying to use Auth0 for the first time and referred sample code from here to create a MVC sample application. auth0-aspnetcore-mvc-samples/Quickstart/Sample at master · auth0-samples/auth0-aspnetcore-mvc-samples · GitHub

I have created the application and have set all the settings as mentioned on the Auth0 starter page as well as the guidelines mentioned here Auth0 and ASP.NET Core MVC (.NET 6.0) Tutorial | by G. Nervadof | Medium. I am using Visual Studio Dev tunnels to test but I am always getting a below error instead of seeing the login or signup page.

InvalidOperationException: IDX20803: Unable to obtain configuration from: ‘’. Will retry at ‘2/21/2024 10:39:46 PM +00:00’. Exception: 'System.IO.IOException: IDX20804: Unable to retrieve document from: ‘[PII of type ‘System.String’ is hidden. For more details, see Bing]’.

I am not sure what could be an issue but would really love to get an insight to resolve an issue.

Thank you so much.

below is the screenshot of the error: