I just wanted to give a heads up that if you have a problem with the technical aspects of file delivery, you need to contact [email protected] to resolve it. I don't have very much control over Gumroad's systems—they're a third party service that I use but don't control—so I can't fix problems. The support people can look at your account and figure out what went wrong.
Also, even though you don't need to create an account to buy something from them, I recommend doing so anyway. It allows you to see everything you've ever bought and download it again if there's a technical error in delivery (or if you just accidentally delete the file or something). Even if you purchased something without an account, if you then subsequently make an account with the same email, everything you previously purchased will show up in your Library.