Cognizant — delay in releasing of offer letter

I had given an interview on 13th july, sb road, pune. Cleared all the rounds and after final hr round, i was told to expect offer letter within 7 to 10 days.
It's been almost a month, still i haven't received the offer letter.
I got auto-generated select mail and to fill cis in one of their portal. I reached out to cognizant hrs, but got no response.