Why did my e-Mandate registration fail?
The eMandate registration may fail if the authentication using net banking or debit card is not successful. This may happen if the authentication window is closed before credentials have been entered, or if incorrect credentials are entered. Zerodha wouldn’t know the specific reason, only the banks will.
If mandate creation fails, they can be recreated from Console, see How do I set up automatic fund transfers from my bank account to my Zerodha trading account?