Pierre Masson has put together an article on the Autodesk Knowledge Network that shows you how to use the Fiddler software to sort out issues with Fusion 360, BIM 360, Process Analysis 360 which will not connect to various websites due to Proxy issues. These connection may be needed on startup or at any time during the usage of the product.
It is not unusual for companies using enterprise level anti-virus to have requests to specific domains systematically blocked. On top of this companies often use a Proxy that requires Authentication, and Autodesk applications make requests in an anonymous manner, so the request are blocked. This results in a software not starting not work properly.
Fiddler is a very useful tool from Telerik to help understand and troubleshoot communication issues for our Autodesk products.
In the screencasts that Pierre has created he shows how to use fiddler to diagnose the network communications and find errors. Please click on the link below to play the videos in full screen so you can see the text.