This should normally not be a problem. You can only register the product 30 days after the date of purchase anyway. And then you have another 30 days. The important thing is that the product was purchased within the promotional period. However, a copy of the purchase receipt and the serial number of the graphics card are required for registration.
PS: So if you still haven't received the product after 5 or 6 weeks, I would cancel the product anyway. Sometimes the price of the product has already dropped during such a long period of time.