I've installed ArcMap 10.3 and want to use Arcgis online from the desktop. At the beginning it was not possible to connect to Arcgis online. The menu was "grey" , so not available. ESRI support gave us some url to reference in our proxy and now we can access to Arcgis online menu. When I launch Arcgis Online, I've got a windows with an error "an erro occurred, check your internet connection" . The problem is that nobody can help us to find the issu. Esri support in France say that it is a problem with our computing infrastructure....
I used a tool "Fiddler Web" to see what happen when we launch Arcgis Online and I see the following url : www.arcgis.com:443
The port 443 is open in our proxy.
In Fiddler these lines appear when I connect to Arcgis online :
... but i don't know how to interpret it. Actually, it is the first time I use it!