ISO country key & is not assigned (header).

What causes this issue?

In the header of the <GL:EDI>EDI</>-intermediate document
<GL:Intermediate_Document>(intermediate document)</> there is an ISO
country code which is not maintained in the global parameters for the
respective country.

How to fix this error?

If the ISO country code should be supplied, make the appropriate entry.
Otherwise you should find out how the unauthorized value got into the
intermediate document.
If you have the authorization, change the ISO country code as required
in <GL:Customizing>Customizing</>.
If not, inform your system administrator.

Error message extract from SAP system. Copyright SAP SE.