When you purchase an ESET product from a retailer, you will receive a product key card in the box and the product to activate it. And if you have purchased the product online from ESET’s official site, you will receive an activation code on your registered email id. When you install the ESET product on your computer, you must enter the product key to activate it. The process is straightforward, but the product key not working in certain situations. Go through our content to learn about the causes and solutions to this issue.