If you are receiving this error message this means that you are trying to log into an Epic account by using a social account such as Google or Facebook. You are restricted from linking social media platforms, if you currently have a Cabined Account, or due to your age and region.
To log into your account, please use your Epic Games credentials or another connected platform.
To learn more about Cabined Accounts check our official EPIC GAMES CABINED ACCOUNTS FAQ.