No PDF file received from OMS

What causes this issue?

When displaying a print document using layout formatting by an output
management system (OMS), the PDF file that is created is sent back to
the IS-U system by the RFC-enabled (inbound) function module
ISU_IMPORT_PDF, where it is received by the initiating process.
However, the receipt of the PDF failed. The system cannot find an entry
for process key &v1& in the temporary storage table for the PDF file.

System Response

Processing cannot continue.

How to fix this error?

Check why the PDF file was not received by the OMS.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.