How to find out why you are not billing?

Hello everyone

We are not able to create invoice, by the process of for a specific student.
The account has correct dates and consistent lines.
In the Billing Standart Request, the Create Account Statements field is marked with the Account Balance Method option.

We made a 255 trace of the SFPBIPRC cobol and when it arrives in step GETSTMT Stmt = SFPBILGE_S_LNNOTBL length = 473 finds the correct item_nbr.
Follows step update
GETSTMT Stmt = SFPBILGE_U_ITEMDT - length = 248
and shortly after in step GETSTMT Stmt = SFPBILGE_U_ITEMDT2 length = 251 undoes the update made in the previous step.
For this student does not call the GETSTMT step Stmt = SFPBILGE_I_BILLHDR length = 1229