Kirkland is a store brand sold by Costco. Which means that you bought the items RETAIL (even though Costco says "Wholesale" in their name, it's still retail in most cases).

Amazon wants you to source from authorized WHOLESALE distributors, and in many cases, to have written authorization FROM THE BRAND to sell their products on Amazon.

On the bright side, Costco has a very generous return policy, so you should have no problem getting your money back. Then once you do that, spend a few weeks reading through the forums and Seller U.

(and yes, there are a lot of sellers selling Kirkland products. For a long time, Costco didn't seem to care, and Amazon didn't question; so for many people there was no approval process. But Amazon is changing, and RA is no longer a generally acceptable method of sourcing product)