Diagnosis
There are three possible reasons for this:
The Billing Engine Application (BEA) in question has not yet beengenerated.
The metadata of the BEA was changed, but the BEA was not re-generated.
This means that the data is inconsistent.

Procedure
RESET N1
Generate the BEA.
Generate the BEA again.
If the problem persists, contact your system administrator.