This usually indicates that your PSN, Xbox, or Nintendo account is connected to a “nameless” Epic account, which can occur when you play on PS4, Xbox One, or Switch without connecting an Epic account. This can be corrected by promoting the “nameless” account to a full-fledged Epic account.
To promote a "nameless" Epic Account, use the steps at the following links:
For PSN, complete the steps here.
For Xbox Live, complete the steps here.
For Switch, complete the steps here.
Bear in mind that all of your save data is tied to the Epic account that your PSN, Xbox, or Nintendo account is connected to, not the PSN, Xbox, or Nintendo account itself. If you disconnect a PSN, Xbox, and Nintendo account from the "nameless" Epic account after promoting it, you will no longer be able to access your progress on PS4, Xbox, or Switch.