Symptoms

When attempting to retrieve users belonging to a manager in K2 Smartforms using the AD Service2 User Smartobject, no users are returned to the 'List Display' control.
 

Diagnoses

After making some changes to map the Control's data source and using the 'populate list control with data rule', the 'List Display' control does return data but only a single result. Unfortunately, this control was as designed the 'List Display' name is a bit deceiving because it actually only brings back one value at a time (not a list as the name implies), but it is called that due to its usage for associated data on List Views.

https://help.k2.com/onlinehelp/k2smartforms/userguide/current/default.htm_SF_-_ViewControls_-_List_Display.html
 

Resolution

The 'List Box' control was used instead to achieve the same functionality.