Could not create delivery schedule

What causes this issue?

The system could not process the delivery schedule sent with the IDoc
because at least one of the following values is missing:
Document number
Document item
Logical system
Delivery schedule number
Delivery schedule type

System Response

The system terminates the IDoc processing.

How to fix this error?

For the current scheduling agreement, check the fields in the table
/SAPAPO/TPSCO for the document number (VBELN), document item (VBELP),
logical system (LOGSY), delivery schedule number and delivery schedule
type that are in the current IDoc to be processed. The delivery
schedule number is in the field LABNK of the IDoc segment E1EDK09. The
delivery schedule type is in the field SCREL in the IDoc-Segment
E1EDP10. The field SCREL contains the value <LS>03 </>or <LS>04 </>for
a forecast delivery schedule and the value <LS>02 </>for an operative
delivery schedule.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.