I just had the same issue and called customer support and found out that Turbotax only guarantees the activation code for 60 days and after that you are out of luck unless you can produce the receipt of purchase. Nowhere on the sleeve that you pick up from Costco does it mention the 60 day timeline and customer service says you have to find that fine print on their website. Customer service has advised that unless I can produce the receipt from Costco, I will have to buy a new product from them. Customer service says that they have no record of me buying the product even though I used the code twice already on the same account to file two other family members taxes. Essentially, extremely unhelpful and too bad and give us more money even though you already paid us once--cash grab!
The activation code is on the back of the card inside the box. It is different from the code on the receipt, you have to scratch the back of the card to reveal it.
If you are still having issues with the activation code, we will be able to help you. We will need more information. Therefore, could you please meet us by private message on Facebook or Twitter to see how we can help you further?