How do I see which work items a rule reassigned?
Open My Rules: each rule's Reassignments column carries a button reading, for example, 8 of 8 passed.
It opens the Reassignment Log, which lists every work item the rule moved and, on a second tab, the ones it could not move with the error each hit.
Related pages
Analytics and Reporting with Out of Office Data - where this is covered in full.
Automations and Workflow - more questions on this topic.
