This article provides troubleshooting steps if users are facing issues in creating cloud backup to mysonicwall account.
The issue has been reported in various NSv and NSA devices where when attempting to do a cloud backup, it fails with an error message, "Failed to upload preference backup file"

NOTE: It's important to create cloud backup. These cloud backups are stored securely on the MySonicWall.com account that the firewall is registered too
Steps To follow:

If above all step are done and all tests pass, and still error message prompts while creating Cloud Backup. Navigate to go to the Diag page.
The Diag page can be reached by typing in the LAN IP of the SonicWall in the browser, with a IP/sonicui/7/m/mgmt/settings/diag at the end.
EXAMPLE: 192.168.168.168/sonicui/7/m/mgmt/settings/diag.


After making all the changes if issue is still there:
Please contact support Contact SonicWALL Support