We agree on that. I do need to fix it. I will go through the article step-by-step. Probably tomorrow; my head is spinning :)
Thank you very much.

>Clearly, WAuth is not working in your app - that needs to be fixed. You need to get HttpContext.Current.Request.IsAuthenticated to be True.
>
>In https://support.microsoft.com/en-ca/help/323176/how-to-implement-windows-authentication-and-authorization-in-asp-net there's a section "Configure Web application for Windows authentication" - have you gone through those steps? Specifically, if your app previously did not use WAuth you might have to reconfigure/rebuild it as described (e.g. step 9) - it looks like just adding the switch in web.config is not enough (?)
>
>Or, can you try building and running the test app as described in the article?
>
>>There is only one way to set up Windows authentication in the ASP.NET page:
>>

>><authentication mode="Windows" />  
>>

>>
>>And I have it set in the web.config. But I have never get the HttpContext.Current.Request.IsAuthenticated to be True. It is always False, on my PC, on one customer network, on another customer network.
>>
>>Therefore the following paragraph of the article never works for me:
>>

>>Using Windows Authentication however enables the remote user to be authenticated (i.e. IsAuthenticated is
>>true) automatically via their domain account and therefore the HttpContext.Current.Request user is set to that 
>>of the remote clients user account, including the Identity object.
>>

>>
>>I don't know what I need to do to have the HttpContext.Current.Request.IsAuthenticated return True.
>>
>>It could be that this is my problem.