Collector for ArcGIS Windows 10 version does not seem to work with Portal
When I try to connect to Portal using the same Url I use on my Android device (https://portal.mydomain.com/arcgis). It goes to some page within the /portaladmin API instead of connecting to our Portal (see image below)
To re-iterate, this works from an Android device so I know our Portal is setup correctly. Also the Windows 10 Collector does work when I go to AGOL
Follow the KB article steps outlined here: 45931 - Connecting to Portal for ArcGIS with Collector for ArcGIS on Windows returns error message "...