Cognizant — offer letter not yet released

Address: Hyderabad, Andhra Pradesh

Website: cognizant

I was interviewed at CTS on April 7th, in Hyderabad for Big Data Developer. I cleared all the rounds and HR told that the offer letter will be released in 10 days but its been more than a month and I haven't received any offer letter. On April 11th, I received an email from CTS talent acquisition to upload my Photo in one of their portal. I mailed the HR who sent me interview call letter many times but no response. Any idea how many days does it take to release offer letter?