This site is being deprecated.
Please see the official X‑Plane Support page for help.
I am not with Laminar Research; just a flight simmer.
You have not indicated the format you have for X-Plane 11.
If you have a disc version there is no product code. You have to have disc 1 of the set inserted in your disc drive at all times for it to run. There is one seller of a disc version that does provide a password but this is a sales gimmick to get you to acquire additional products from them.
If you have a digital download version from Laminar Research you will need to provide date of purchase, possible receipt number, details on how you paid for the product and more important the exact email address you used at the time of purchase. If this is the method of acquisition of X-Plane then have a look at the following link at http://www.x-plane.com/support/ for contact details to solve your problem.
This site is no longer being actively maintained.