Valid owner object passed (field APPL_KEY)

What causes this issue?

The address reference transfer structure APPL_KEY field was not filled.
The application object key is entered here in the composite form Client
+ (BOR) object key.
Example:
The APPL_KEY '001US02' is passed for company code "US02" in client 001
When the key is concatenated, no spaces must be lost if the key is
assembled from several fields.

System Response

The System cannot assign a number for this address as no valid
reference was specified.

How to fix this error?

Pass the field as specified in the function module parameter
documentation.

Error message extract from SAP system. Copyright SAP SE.