Cognizant — did not receive the offer letter yet

Address: Khordha, Odisha, 751024

I attended an interview of cognizant held in bhubaneshwar on 16th feb 2019 for msbi developer i got selected and the hr informed me that i will be getting the offer letter in 15 days time. After a week i received a mail from talent acquisition for uploading my photo and some basic details in a portal after that i received a call on 12th march from hr team in the call i was informed that i will be receiving the offer letter shortly but it's been more than a month i have not received the offer letter yet meanwhile on 28th march received the same mail from talent acquisition for uploading my photo and some basic details in a portal. I tried to reach cognizant hr team but there is no response from them.
I am not sure if normally they would take more than a month to release the offer letter.