When you search for invoices between dates, the results list sorts by name by default. If you sort by date, find an invoice, then click in to review it, and then return to the Find Invoice Results screen, the results revert to sorting by name.
This is working as designed. The sort isn’t saved, and workers can’t currently set a default sort column. If you think saving sorts would be useful, you can raise an idea or vote for one on our Aha ideas portal.