Cognizant — no offer letter

Address: Hyderabad, Andhra Pradesh, 500032

I had attended interview with cts back in may 2018. They told me i was selected and called me after 2 weeks asking me to go to the venue and submit further documents (Xerox copies). However the offer never came in. I did not have the energy to continuously follow up with the hr (After my e-mail to vaishnavi went un-answered) so i let it go, and decided never to interview at cts again. Now last week they (Cts talent acquisition) sent me a mail for photo upload, after a close 6 months. I wonder why?