This is probably a simple mistake somewhere, but when I try to add an external MapServer service (meaning created/hosted by some other site) to an ArcGIS.com map when I'm logged in to my Organizational account, it acts like it can't see the service. However, if I log out and create a map on ArcGIS.com without signing in, I can view the service no problem.
I'm the Administrator for my Organization, so surely it's not a permissions issue, right?
Any ideas?