Hi,
Please make sure Firewalls/proxy server should allow Web Service URLs both secure and non secure ports (80 and 443) to access Web Services from your network.
To make sure you can communicate with the appropriate servers, please trying using the ping -a command on the following addresses:
http://rendering.360.autodesk.com
For example, the command should look like this in the command line (Windows Key +R, enter CMD)
Ping-a rendering.360.autodesk.com
(More reference: http://knowledge.autodesk.com/support/autocad/troubleshooting/caas/sfdcarticles/sfdcarticles/AutoCAD...)
Please try to go through the following process:
1. Close all browsers and any other apps connected to the internet.
2. Close Revit.
3. Go to Control Panel > Internet Options
4. Clear the Browsing History, including cookies and the cache.
5. Clear the Temp folder (Hit Windows+R, Enter %temp%, clear folder).
6. Launch any browser.
7. Launch Revit.
8. Try to sign into A360 within Revit.
Hope this helps.
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