My Product Came In Defective
Ugh. This is the worst.
When this happens, you'll need to contact the seller to let them know. They might be able to get you a new product, or solve the problem for you, from their end.
And you can find the seller's contact information next to the product in your selected deals page, or in your original approval email, saying the seller okay'ed your request to buy their product at a discount.