Why Importing Users taking very long time and finally importing nothing in orchestrator

Scenario:Importing Users in Orchestrator using Active directory

Steps to reproduce:

Current Behavior: No user groupd were imported

Expected Behavior: Imported users

Studio/Robot/Orchestrator Version: 2016.2.62

Last stable behavior:
Last stable version:
OS Version: Windows windows 2012 r2
Others if Relevant: (workflow, logs, .net version, service pack, etc):