We currently have multiple installations of ArcGIS for AutoCAD build 350 that we have set up to pull in services from our secure internal ArcGIS Server (10.2.2 with AD Authentication on the web tier). We haven't run into an issue until the last install where the user is unable to connect to the AGS. We've verified his credentials and tested his ability to connect to the rest endpoint in multiple web browsers. When setting up the connection to the AGS in AutoCAD (Civil 3D 2015), he is continuously prompted for credentials and authentication fails.
We have not had this issue with any of our other clients on identical machines (Windows 7 64bit).
Does anyone have any ideas? AD Authentication being successful in multiple browsers yet failing within AutoCAD leads me to believe its an AutoCAD setting or an issue with the extension. I've reinstalled the extension multiple times without any success.
Any help is greatly appreciated,
Shaun