Hi,
I just wanted to update you that we resolved this particular issue with Skyline support team. In case you're interested, the fix is to add the Site: Guests user group to the Reader role. When Skyline is connecting to Panorama server, even though you give provide user account and password in the connection preferences, it doesn't use this information for initial check of the server. Of course, it does use the user log-in credentials to upload to the server.
They may address this in future version of Skyline but this is the workaround for now.
Monica