I've recently installed GIS Server 10.7.1 within a corporate network which has limited access to the internet (an internal forward proxy can be used for application-level configuration). I've seen and followed the documentation at https://enterprise.arcgis.com/en/server/latest/deploy/windows/using-a-forward-proxy-server-with-arcg.... The only thing we cannot do, due to corporate policy, is configure OS Lan/proxy settings. But the ESRI documentation doesn't mention that configuring OS proxy is required, which leads me to believe the built-in proxy settings (under arcgis/admin) should work by itself. However, after setting this configuration to our forward proxy, GIS server doesn't appear to use these settings (e.g. with custom Print service retrieving basemap). I've confirmed with our Proxy/network team that no traffic comes through. However, I can successfully make a web request (powershell "wget") using the internal proxy from that same server. Does anyone have a fix? Or has anyone else encountered this same issue? Any help appreciated.
P.S. Server logs in manager reveal the following message, for example:
A connection with the server could not be established (WinINet Error while using HTTPS security, 12029), URL = http://services.arcgisonline.com/ArcGIS/rest/services/World_Terrain_Base/MapServer?f=json