Assign each wrestler to a weight class in the tournament event via Weigh In Wrestlers. Otherwise, Takedown does not know the weight class in which a wrestler is competing.
If your Takedown LIVE tournament matches don't have a weight class for a match:
Go to the tournament event and tap Weigh In Wrestlers. You need to assign each wrestler to a weight class for the tournament.
Alternatively, you can enter the weigh in for each wrestler and Takedown will auto-assign the nearest weight class. You can override this auto-assignment by tapping on the weight class.