hmmm. i used just just click the "enroll" button for new games. But I can't find it anymore! No one else has this problem? It seems that more people are only playing 1 game at a time. But this might be a coincidence.
You can still playing two games at the same time, but one game is considered finished when the game is totally over, even if you are evicted before the 7th day. It may happen that you get evicted from 2 games, i.e. in day 1 and you have to wait 6 days to enroll again as both games are not finished yet.
I just joined a new one last night and still in Rookies too :)
Hope it works out for ya!