Epic Games is requiring that users have two-factor authentication activated in order to claim free downloads, until May 21. The Fortnite developer said in a blog post that this was to help protect account security and is presumably because more people are downloading more free games at the moment.
If you do not have two-factor authentication enabled on your account, you will see the following message when attempting to claim a free game: “Two Factor Authentication Required Claiming this free game requires you to have Two-Factor Authentication setup on your account. Two-Factor Authentication provides an additional level of security to your Epic Games account and will help prevent unauthorized access.” In order to enable two-factor authentication, please head over to your Epic Games Account settings. Two-factor authentication can be used to help protect your account from unauthorized access by requiring you to enter a security code when you sign in.