Power BI with oAuth2.0 login

I want to implement oAuth in power bi and for this I follow the steps using the following available links.

https://docs.microsoft.com/en-us/power-query/samples/github/readme

https://docs.microsoft.com/en-us/power-query/samples/mygraph/readme

 1. In my code, a login screen of azure is display but after successful login, a blank webpage is display and I am not able to get the access token.

 2. In my second try, I only use the API which return "access token" and I used it as a data source in power bi desktop application. In desktop application, I used the other endpoints to get data, using the access token provided by connector and upload it on power bi service.

 In service side when I add this on gateway, the following errors are occurred