This article explains how to move the registration of a contract which has been applied against the wrong serial number. Solution
The Service & Support Web Portal does not currently allow contracts to be moved between devices.
If a contract has been registered against the wrong device then it is necessary to login to https://support.fortinet.com and create a Customer Service ticket. Set the category to CS Unit/Contract Transfer.
Indicate the contract number, the device serial number it is registered to, and the unit serial number to which it is to be transferred.
Attach the Contract Letter, this is required by Customer Service for verification purposes.
Customer Service will process the request and notify you when completed. Customer Service will inform you of any exceptions in the event that one or more contracts cannot be moved.