The AutoDesk Clean Un-Installer application should be upgraded to report its failure to remove registry keys associated with Fusion 360. The relevant keys should be listed in the application's log file. Succinct instructions should be provided indicating how to address the registry key removal problem. In my experience with this issue, it appeared that Windows Defender had blocked the Clean Un-Installer app from removing registry keys, but the app nevertheless reported success. Subsequent attempts to upgrade Fusion 360 failed until an AutoDesk support engineer manually removed the offending registry keys. (Customer support was excellent.)