I had the same problem but found a solution!
Here’s what I did to receive the email invite to join the EpicGames GitHub repo.
I created a new email address and then created a new GitHub account and a new Epic Games account with it.
Followed the steps to connect my Epic Games account with GitHub but this time I made sure to select the option “Unreal Engine End User License Agreement for Creators” when prompted to accept one of the 2 license agreements.
I suggest trying these steps with your current account first, if that doesn’t work try creating new accounts as I did.
Good luck!