An empty preview on a scheduled or pending task is normal. A completed task should show the file.
Refresh History and open the task after the status changes to completed. The preview is part of that completed record.
Match the message to the status
- Scheduled: no file yet
- Pending: still working
- Completed: preview should be there
- Failed: read the error instead
Also check that at least one section was checked. A task with every box off has little or nothing to list.