Approval Levels, system is not assigning the first approver

We have a trouble right now with approval processing.

We understand that approval proc begins when the user creates new orders, then the system assigns the approval routing and with this approval routing determines who is the first approver.

We have this scenario:

1. We have defined levels for each approval routing, so we have a route named FCAS001 and into this approval levels we have defined 3 approvers.

2. The system is not assigning the correct first approver, so when we check the F4209 table the system is assigning the last approver and in the worst scenario is assigning zero value in the HORPER field.