Cognizant — offer letter - need response

Dear all,

I attended an interview at cts thoraipakkam on december 1st 2018 under rpa domain [uipath] and cleared technical round after that they provided hr form and filled that one too. At the end hr round he informed me that i will receive my offer letter in 1-2 week but i haven't received yet. I only depends upon this offer letter. What might be an issue? Is this any related to exp wise or else package wise if i get any clarity on this i will take it up and apply for future.

Please help on this