Cognizant Technology Solutions — regarding offer bgv

Address: 560700

I had interview on dec 16th and completed two rounds of interview on that day and i got interview status as selected, i got my offer letter on 24th dec, after accepting offer in pre joining mail am not redirected to background verification (Bgv), it shows you are not authorized to access this application still am not uploaded even one document also how to solve my issue please help me