What causes this issue?

Valuation is at company code level. However, inconsistencies have
arisen because of the way in which the company code was configured in
Customizing or because plants have not been assigned to a company code.

System Response

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

How to fix this error?

INCLUDE NA_SYSTVERW1


Procedure for systems administrators.
Check the assignments of plants to company code.
<DS:TRAN.OX18>Proceed</>
Check the configuration of the valuation level.
<DS:TRAN.OX14>Proceed</>
If the assignments are correct, check and correct the entries in table
T001K.
<DS:TRAN.SM31>Proceed</>

Error message extract from SAP system. Copyright SAP SE.