How to resolve error: This serial number is already used on NSv Sonicwall firewalls.

You might encounter this error in environments where you are re-deploying the NSv virtual machine or transitioning from a TRIAL free version to a production license.

Error: The serial number is already used.

Resolution for SonicOS 7.X

This release includes significant user interface changes and many new features that are different from the SonicOS 6.5 and earlier firmware. The below resolution is for customers using SonicOS 7.X firmware.

1.- Deregister the current licenses from the firewall:

Navigate to Device | Settings | Licenses.

2.- Reset the license from the diagnostic page and internal settings. Note that this could cause a firewall reboot.

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/diag    +  Internal Setting

Click the"Reset Licenses and Security Services Info" button and then click "Exit Internal Settings" at the top of the page.

https://www.sonicwall.com/support/knowledge-base/licenses-not-synchronized-with-mysonicwall-resetting-the-trust/170503759160983

3.- Disassociate the GUID number, associated with the existing unit from mysonicwall.com and Product Details:

- If you still see a GUID number and it is not possible to remove it, please contact SonicWall Support using our phone support and ask for the removal of the GUID associated with the existing firewall unit.

- After that, you should be able to register the unit using the mysonicwall user/password where the device was registered.