ATG 8, expansion only card set

I have been trying to join this league; https://365.strat-o-matic.com/league/438785


I have tried both ATG 8 and ATG 8 post WW-2 league settings when building my team but neither qualifies for this league when it comes time to "join a league" .

I don't see an option to choose ATG 8, expansion only when starting a team. I'm hoping I'm missing something obvious. Appreciate any insight from the group. Thanks

scroll through the "Shuffle the Deck" box under ATG8 - it's in there...

Thank you