There can be a few reasons to explain such a case:
- One reason could be failed internet connection at the time you tried to make the payment.
- Another reason could be that the payment gateway is unable to get any response from your bank during a transaction.
- Insufficient funds in your bank account can also cause payment failure.
- Do check whether or not your online banking is activated because that can also disrupt a payment process.

If you're still not sure of the reason, you can easily file a ticket at with your transaction details and be assured that your issue will be resolved promptly.