Cognizant — received offer but getting delay in onboarding

Address: Kanchipuram, Tamil Nadu, 600045

Hi i have attended interview in cognizant on dec 2017 and got offer letter on jan 2018 and my doj was 4 thapril 2018 but my onboarding pass not generated till eod on doj but till now they have released 3 offer letters of different date and still not leaving me to get onboarded.2month they took to complete the bgv and after getting relived now they are saying bgv not cleared as one of my company closed 3 years back itself and dnt have any details apart from offer letter resignation letter. Not sure wat they are still looking when other companies have accepted it and i worked there for more than 5 yeras