With the new installation of Build 400 I am unable to connect to my Portal environment, but I can join my company's ArcGIS Enterprise account. When connecting to Portal, the contents just say loading and eventually times out with an AutoCAD Unhandled Exception. That being said, I am able to load data using the url rest endpoint. I am currently using AutoCAD Map 3D 2018. Attached are the Images of what I am experiencing. Has anyone else had these issues? arcgisforautocad
Wow, that's ugly. No, I haven't heard of others having this problem. There could be something unique in your Portal environment that isn't working well for ArcGIS for AutoCAD. A call to technical support might pin it down.