HDFC Bank — Not receiving OTP on email

I have to reset my net-banking pin. There are 2 options :

1) registered number + debit card — i can't use this because I cannot remember my debt card PIN as I was not using it.

2) registered number + e-mail : the 3 digit otp comes to the registered number but the email never arrives, i don't know why, already raised a complaint with the bank.
Complaint number: MUMC[protected]