Not possible to add teams to (American) conference

I currently only have 10 teams in the American and when I try to add a team there in custom conferences, it says I’m unable to. I’m in custom conferences before the first season of road to glory. Keeps saying I have divisions when every time I try to turn divisions on, it reverts to off. 

Every other conference works fine outside of the renaming glitch that takes a few tries. Every other conference has 12 teams, 15 in independent currently when I’d like it to be 13.