Craftsman ZT7000 stoped going in forward or reverse

Hello, I just purchased a used ZT 7000 22HP 50" Cut mower. Grandaughter rode it for about an hour last night, and today I was mowing fine: then all of the sudden it would not go in forward or reverse. Belt is still on: the rods to disengage the transmission were not moved. Any idea's????

Replace the drive belt. The only thing that can affect both drives at the same time is the drive belt. Before you replace it make sure the tensioner pulley is still connected to the spring.