Drupal - Ubercart file download link not working from e-mail

I have Drupal 6 installed with Ubercart 2.0.

When an anonymous user purchases a product from Ubercart, a new account is automatically created for them and they are emailed a link to download the file associated with the product.

The link doesn't work unless they are logged in, which does not happen for them automatically.

I need one of the following two things: Either the user should automatically be logged in, or the file download link should work even for anonymous users. I am not sure how to go about doing either of these, so I would appreciate any guidance.

It turns out there's a checkbox in the Ubercart settings to log the user in after checkout.