John van der Berg medal 5000 4 years 334 days ago
Ironically, you need to have enough rookie managers in your league that it will be shown to anyone. That's not just the case for rookies, but for pro and elite, too, though. You need to/should maintain at least 12 to 13 managers in each tier. Then you have a good chance that your league will appear to people who are searching for open spots. At least to those who also match your racetime in their search and the 1/2 car filter.
I hope that explains it to you although it's perhaps not really helpful atm. Maybe put 3 or 4 rookie teams of your own in rookie to get the league jump-started again. You can remove them later on when the tier is filling up again.