Why my credit card was not accepted by webstore?

Some national debit cards/credit cards are not activated for international online transactions by default.

E.g. If you have an SBI bank, just visit sbicard.com or the SBI Card Mobile app, log in to your account by entering your username or password and select ‘Request > Activate International Usage’ from the left menu. You can write your bank name (sbi, axis, hdfc, Kotak, citibank, etc) to support chat and receive on-screen instructions how to enable international transactions. Alternatively contact your bank or consider to use Prepaid Virtual Credit Card (VCC) if you have. Virtual credit cards are the best and most secure option for making payments on the web.