Hi Hilary Curtis,
I am attempting to work through this same problem. collaboration portal_for_arcgis arcgis_online portal
The Portal Admin log shows this:
The Guest (Portal) shows this:
The Host (ArcGIS Online) shows this:
...
...
My Portal (Enterprise) install is NOT internet accessible (intranet) but it is configured correctly to pass through our enterprise proxy. It is also configured with Domain Certificates. It is secured through Active Directory. Roles and Users are managed through Portal.
The ArcGIS Online side of this collaboration is configured to use a resource account that is in the Active Directory and registered as a Portal user. Right now, the collaboration has that User ID as: user1@DOMAIN, as the user is listed within Portal. I am wondering if it needs to be changed to DOMAIN\user1.
Looking at the Admin Log - in the "USER" column - I am wondering if it is even getting credentials....
Any ideas would be great!
Thanks,
--Adam