CEO & CTOHi! There's a bug that I don't know if it's personal or if it happens to everyone, but I have a level 7 account that I used to try sprint races, and although it now lets me click on the "Leagues" option, my account profile says I'm in beginner mode, so no leagues appear in the search engine and it doesn't let me join one.
This should be resolved now. I forgot to bump everyone up who was already level 7-10! The game wouldn't automatically do that. Thanks for bringing it to my attention.