Dot net core api - unwanted /oauth2/default getting added

Hi, I am securing the web api by sending the AccessToken to “” url in web api config. I can see below errors in output window. I am getting extra “/OAuth2/Default” in url(please check second paragraph). How I can remove that from URL and get rid of this issue

System.InvalidOperationException: IDX20803: Unable to obtain configuration from: ‘[PII is hidden]’. —> System.IO.IOException: IDX20804: Unable to retrieve document from: ‘[PII is hidden]’. —> System.Net.Http.HttpRequestException: Response status code does not indicate success: 404 (Not Found).
at System.Net.Http.HttpResponseMessage.EnsureSuccessStatusCode()