Sony generally sets their codes to expire after 2 years. That code was generated around the end of 2018, more than 4 years ago. Unfortunately, there is a difference between an item being unopened and an item being new. You were sold a product that had an expired code in it. You'll need to request a refund from the retailer that sold it to you, as you effectively paid for just the disk of Destiny 2, which is now free digitally with no disk required.