FM account assignment is missing from business partner line item

What causes this issue?

You want to post a document that is recorded in Funds Management. To do
this, you must assign an FM account assignment that contains at least
the relevant company code (and therefore the corresponding
<DS:GLOS.3528EACDE8AA5570E10000009B38F983>FM Area</> in FM as well), a
commitment item and a funds center.
In this document, the FM account assignment is incomplete.

System Response

The document cannot be posted.

How to fix this error?

Complete the FM account assignment data and repeat the posting
transaction.

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.