Link Xbox one to epic account?

Has anything changed in this process? My buddy has an xbox one, I pc. We want to play Fortnite and connect his Xbox live account to his Epic account. If we're now ready to enter the Microsoft Xbox Live login data on the Epic page, it says that the login data is incorrect, but his Xbox logs into the live account as normal when it starts and he can play Fortnite with it. But just linking does not work. Any idea?

Try this either via the browser, on the main website, if Epic has something like this, or link the account to another game when Fortnite is messing around. Dauntless is also an epic game, and you should also be able to connect when you register.

Ok thanks.habs already tried in a browser.