Nasdaq interview questions

There were total 5 rounds, 3 technical and 1 hiring manager and 1 HR. I cleared all the technical rounds, hiring manager round also went extremely well, even the manager said after the interview that “see you at Nasdaq”, still after 2-3 days, I got a mail that you won’t be able to clear that round. I was completely in shock as I don’t even know where it went wrong. Tip to the HR: Let interviewees know the reason why are you rejecting him/her even his/her interviewer told only good things about them.