Symptoms
After attempt to sort the orders (from All Orders tab) by the some filed, search items disappear, additionally there are no more navigation links (20/50/100), no more possibility to view the next page with the orders.
Cause
The issue is caused by the bug with id #PBA-80981 ("On the tab All Orders links "Pages" and "On page" disappear when the field "Status" is empty.")
Resolution
As a workaround (until the bug is fixed) sort the orders by "Status", navigation links must reappear.