Hi @gagan02 ,
could you please try to increase timeout and see if that works.
please check below link and see if it helps you to resolve problem: Timeout Errors and Settings
You need to use the Partial Source Update (https://developer.sailpoint.com/idn/api/v3/update-source ) API to modify the timeout value.
Also check your VA is in connected state and the ccg version of VA is available in ISC.
If still not working try to IP address of the AD server
I found similar issue here: Timeout Error When Connecting SailPointNow to Active Directory - #12 by MisalRohit