If you are trying to log in to an Epic Games account in your browser and you keep getting logged into the same or wrong account when you opt to log in using third-party credentials (i.e., Xbox, PlayStation, Nintendo, Steam, etc.), try clearing your browser's cache to troubleshoot the issue. After clearing your cache, retry logging in.
You can also log in to your account in an incognito/private browser window to prevent your browser from autofilling your third-party log in credentials.