You'll need to compare the sort order produced by this script step:
Sort Records [Restore ; No Dialog]
with the "sorted by" settings for each sub summary layout part. The field specified as the "when sorted by" field must be included in the sort order specified in your script step or it will not be visible.
You can double click the layout part label to open a dialog box where you can see what field is specified as the "break" or "sorted by" field.
That worked. Thank you!