My agency has an Internal (local DNS'd) ArcGIS Enterprise platform and we are not being able to connect. All other Apps such as ArcGIS Pro are able to see our portal endpoint (prodgis.dor.wa.loc/portal) ; but the plug-in tells us "The specified ArcGIS (or ArcGIS Enterprise) URL is not valid.
Is this locking up on the internal/non-externally-routable DNS? We are totally SSL and Cert based running across 443/
