I am getting a lot of great stuff working here, and I'm delighted (my client will be, too), but I have the following shortcode in my form, and it's still sorting by ID.
[app_services select="<h3>How long do you need a sitter?*</h3>" order_by="duration" autorefresh="1"]
I have also tried
order_by="name" and adding DESC to each. None yields any change.
I'm attaching screenshots because the pages in question are protected by Membership 2 Pro levels.