Recently, Epic Games rolled out a change to their account system aimed at protecting the younger people on their store and it has caused issues for the Heroic Games Launcher.
Epic announced a change in a blog post recently, for their new "Cabined Accounts" that provide "a tailored experience that is safe and inclusive for younger players while maintaining access to the gameplay you love in Fortnite".
A side-effect, is that the cross-platform free and open source Heroic Games Launcher can seemingly no longer download games unless you do this, leading to people believing that the issue is Heroic breaking. What you'll need to do, if you use it for Steam Deck or Linux desktop, is to either log out of Epic on Heroic and log back in which should bring up the prompt to add your date of birth, or add it on the Epic Games website to your account there.
That should get you back into working order if you didn't have it there already.