Purchasing organization & not responsible for plant &

What causes this issue?

The <GL:purchasing_organization>purchasing organization</> you entered
has not been defined for the specified <GL:plant>plant</>.

How to fix this error?

INCLUDE EINGABE_PRUEFEN_NA LANGUAGE EN
INCLUDE SYSADMIN_NA
The system administrator can assign the purchasing organization to the
relevant plant in Customizing for Purchasing.
<DS:SIMG.SIMG_CFMENUSAPCOX17>Assign purchasing organization to plant</>

Error message extract from SAP system. Copyright SAP SE.