In some cases, this issue is perpetuated by network connectivity issues. Potential root causes could be conflicting 3rd party softwares running in the background, or network restrictions from a proxy server. Below are some suggestions that may help.
For anti-virus software, it may help to add an exception for the Fusion360.exe and the adcefwebbrowser.exe located in the subdirectories of the below directory:
C:\Users\<Username>\AppData\Local\Autodesk\webdeploy\production\<product ID>\...
Manually reset the Fusion network preferences:
1. Close Fusion 360.
2. Browse to C:\Users\<user>\AppData\Roaming\Autodesk\Neutron Platform\Options\
3. Delete the file "NMachineSpecificOptions.xml" to give a try
4. Restart Fusion 360
Toggle Proxy detection settings:
Mac OS
1. From the Apple menu, select System Preferences
2. Select Network
3. Select the correct network (ethernet, wireles, airport, etc)
4. In the Proxies tab, enable/disable Auto Proxy Discovery
5. Apply changes and retest
Windows
1. Browse to Control Panel\All Control Panel Items\Internet Options
2. In the Connections tab, select LAN settings
3. Try to Enable/Disable a Automatically detect settings option
4. Apply the changes and retest.
There are some additional suggestions in the below solution articles.
https://knowledge.autodesk.com/support/fusion-360/troubleshooting/caas/sfdcarticles/sfdcarticles/Dat...
https://knowledge.autodesk.com/support/fusion-360/troubleshooting/caas/sfdcarticles/sfdcarticles/The...
https://knowledge.autodesk.com/support/fusion-360/troubleshooting/caas/sfdcarticles/sfdcarticles/Dat...
I hope these suggestions help, please let us know if you have any questions. I would be very interested to know if any of these solutions works for you (and which one it was).
Thanks,
Nathan Chandler
Principal Specialist