Managing ranked team questions

So I have 2 available slots on my ranked team and am only inviting one player to fill one of those two slots. However league won't let me invite that player and I can't find out why. The player is level 30, ranked, on my friends list, and is on only 3 other teams. When I looked up requirements to being on a ranked team, it's says they have to be level 30 and can't be on more than 5 teams. SO what am I missing? Why can't this player join me?