System.InvalidOperationException

I am trying to use PowerBI Embedded resource from MS Azure to embed an report on client application. I am following steps delineated on this link : https://docs.microsoft.com/en-us/power-bi/developer/embed-sample-for-customers#embedding-for-your-customers

Following are the system details:

• MacOS High Sierra (version 10.13.6)
• Power BI web version is used to create a workspace
• Visual Studio mac version: https://visualstudio.microsoft.com/vs/mac/
• PowerBI pro license subscription
• MS Azure subscription

I have generated group ID and report ID from PowerBI workspace using web version (and not desktop). I also registered  a new app in azure and generated an application ID for it. After providing all the required information in web.config file, when I tried generating token using AppOwnsData git repository (https://github.com/Microsoft/PowerBI-Developer-Samples) getting an error as shown herewith.

Is there any configuration issue? Is it possible to do all these steps on MacOS? Any help to resolve this issue is appreciated.