Hello,
If your GitHub account is a member of the EpicGames organization, then I would expect that you would be able to see the repo. Let's see if we can troubleshoot.
If your account was previously added to the 'EpicGames-Mirror-A' org, I believe that Epic was going to migrate them over. To check what organizations your account is associate with, click on your profile icon and open the organizations page-
In the list of organizations, you should see 'EpicGames' and nothing else-
If your account is only associated with EpicGames, then I wonder if something might have been cached. You could try logging out of GitHub, clearing your web browser's cache (in Chrome select Delete Browsing Data and choose 'All Time' from the dropdown menu).
Sorry about the trouble. Please let us know if you try that and you're still directed to a 404 page on github when you try to access the repo.
Best,
Adam