I removed a second pay run, but now I no longer see documents from the previously processed first pay run. How is that possible?
By processing the second pay run, the documents from the previously processed pay run are archived. You can thus find these documents in Documents as 'archived'.
You can make these documents 'active' again. Celery cannot do this automatically because users can also archive documents themselves, which do not have to be made 'active' again.