Enter a true account assignment relevant to cost accounting

What causes this issue?

All the account assignment objects entered are either all statistical
objects, are posted in CO with statistical values only, or you have not
specified a CO account assignment.

System Response

Statistical postings in CO are ignored in FI-CO reconciliation. You
must enter a CO object for each CO posting to which costs or revenues
can be posted.

How to fix this error?

Enter a CO account assignment that is not statistical.
Possible account assignments are:
INCLUDE 'CO_KONTIERUNGEN' OBJECT DOKU ID TX
Revenue elements are always updated as statistical values when posted
to cost centers.

Error message extract from SAP system. Copyright SAP SE.