If your payment is failing multiple times, it could be due to the following reasons:
1. If you are attempting to pay by a Debit card for the monthly membership, you would see an error that states that "recurring payments are not supported". Since the monthly membership is auto-renewed, you cannot pay using a debit card. You can pay using Zerodha funds or by Credit Card.
2. If you are trying to pay using a foreign (non-Indian) card, the payment will not go through as international payments are not supported as of now.