I have two PNRs for my reservation made thru ANA award flights. One PNR is ANA PNR and the other one is Vietnam Airlines PNR.

I tried to confirm my PNR on Vietnam airlines website to check if I can select the seats. But it requires PNR, Name and e-mail address. What can I do if my reservation is not tied to the e-mail address?
I’ve never seen the site requires e-mail address for reservation confirmation before. The situation is the same with VN mobile app.