I'm running latest Windows Creator Update with IE 11. I've made a web site which returns a pdf. The PDF shows fine. And works in IE 11, Edge, Chrome, and FF. I'm using Adobe Acrobat Reader DC. However, in IE11 only, the tab shows some sort of 401.3 error message. Don't know why as PDF DOES show so it must be able to read it. The web is an asp.net 4.6.1 IIS 10 application. The application does a Response.Redirect to the PDF. When I look at the traffic in Fiddler or IE's built-in debugger, neither shows anything about a 401.3. Does this symptom ring any bells for anyone?
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