?
I see, in that case, your network/server is not properly configured. This is not trivial to troubleshoot, and this is happening before the request hits our software.
The most likely culprit is an invalid/missing SPN, and a domain administrator must add that.
Here are some additional resources to follow:
https://support.microsoft.com/en-us/kb/969060
http://www.sidesofmarch.com/index.php/archive/2011/11/04/troubleshooting-windows-authentication-in-iis/
http://serverfault.com/questions/341978/troubleshooting-windows-authentication-problems-no-challenge-in-iis-7-5
Search terms, "diagnosing windows authentication iis"