IBM India — Delay in releasing offer letter

Address:

Manyata techpark, Banglore

HI,
I attended IBM interview at Bangalore in April 2021.This call is directly from HR.I have cleared technical rounds, Manager and HR round also.In HR round they finalize my salary and submitted soft copies hard copies of all requirements. They assured that you will get offer in 15 working days, Now its more than a month and no words from IBM. During 1 month most of time try to contact HR, but he never received my call or replied to any one of the mail.
Is there any chance to get offer letter from IBM. Do anybody had same experience from IBM in April 2021 interviews conducted at IBM Bangalore? Please reply.