When you have locked your divisions and launched your league round, there are certain settings and changes in the system that cannot be made. This is due to the complexity that a league system entails, and you are later able to make those changes between rounds (before launching next round).
Actions that are not possible in an ongoing round:
Removing a team from a division
Adding a new team into a division
Switching out the players in a team
Moving a team between divisions
Adding a result without the match existed and reached its end time in your schedule