Play on another PS4 with a fortnite PS4 account?

My son has now bought his own PS4 and wants to "take his" Fortnite Account "with him"! The problem is, however, that we ONLY want to transfer the Fortnite account to his PS4 … However, he previously played fortnite on his laptop and set up an Epicgames account with the same email address. He also bought something on the account. How should I connect the PS4 account to epicgames if there's already an epicgames account with this email?

If you are sure that you know the right email and password, you could try to log out of the pc

Select the account from the dropdown menu at the top of the page. Go to the Connected Accounts tab and click "Disconnect" on the console account you want to unlink (in this case: Nintendo Switch).