SCB indicator is missing or invalid

What causes this issue?

The SCB indicator must be filled using a key which has been assigned a
payment reason for the reporting of the house bank to the central bank.
The payment reason for the house bank is stored in the second line of
the payment reason of an SCB indicator.

How to fix this error?

An SCB indicator for which a valid payment reason for the reporting of
the house bank has been defined, must be entered in the document. The
payment reason is only specified in the second line of the payment
reason of an SCB indicator (<DS:TRAN.OB43>Proceed</>).

Error message extract from SAP system. Copyright SAP SE.