The Order number doesn't activate a product, if you select the "Register Serial" option of the Addon Manager, it asks for your Serial Number, which is a longer code that is listed in your purchase receipt.
If you lost it, there's a way to retrieve it, as explained on our FAQ page:
http://www.fsdreamteam.com/faq.htmlI have lost my Email receipt, how can I reactivate my product ?
You can go to Esellerate support site here:
http://store.esellerate.net/supportYou can retrieve your Order History, by inserting the email you used to purchased the product, then press the "E-Mail Order History" button. Having your Order, will allow to use the server-assisted Reinstall.
Pay specific attention to this:
If you want to know your Serial Number, insert your Order Number and Email, then press the "Submit" button on the Esellerate support site: this will enter inside your Order Page, with option to see your original Email Receipt, that contains also your Serial Number.