POR Mapping Set Based Rule Evaluation Failed

Summary:

POR Mapping Set Based Rule Evaluation Failed

Content (please ensure you mask any confidential information):

I submitted a purchase requisition.

In the Transaction Console, the status was shown as "Submitted", but the Assignees field was not set, meaning the request had not been routed to the appropriate approver.

When I generated a diagnostic report, there was no error per se, but the final line displayed the message:
"POR Mapping Set Based Rule Evaluation Failed."

Could you please advise which settings in the BPM Worklist I should review to resolve this issue?