Cognizant — Offer Letter not released Even after selection

I had given interview in cognizant and got selected in technical round.
I got mail from HR that I am selected and need to fill the CIS form and sent back.
But when I sent CIS form I did not receive any call back for further discussion. Recruiter is not responding to my emails, messages, calls.
Literally mental torture.
At least they should communicate what the problem is.